5&#39; triphosphate oligonucleotide with blunt end and uses thereof

ABSTRACT

The present invention provides an oligonucleotide which is capable of activating RIG-I and inducing an anti-viral, in particular, an IFN, response in cells expressing RIG-I. The present invention further provides an oligonucleotide which is capable of activating RIG-I and which has target gene-silencing activity. The oligonucleotide of the present invention has a double-stranded section of at least 19, preferably at least 21 bp, at least one 5′ triphosphate, and at least one blunt end which bears a 5′ triphosphate. The present invention further provides the use said oligonucleotide for inducing an anti-viral, in particular, an IFN, response in vitro and in vivo. The present invention additionally provides the use of said oligonucleotide for preventing and/or treating diseases or conditions such as infections, tumors/cancers, and immune disorders.

FIELD OF THE INVENTION

The present invention relates to the field of immunotherapy and drugdiscovery. The present invention provides an oligonucleotide which iscapable of activating RIG-I and/or inducing an anti-viral, inparticular, an IFN, response in cells expressing RIG-I. The presentinvention further provides the use of said oligonucleotide for inducingan anti-viral, in particular, an IFN, response in vitro and in vivo. Thepresent invention further relates to an oligonucleotide which has bothgene-silencing activity and is capable of activating RIG-I. The presentinvention additionally provides the use of said oligonucleotide forpreventing and/or treating diseases or conditions such as infections,tumors/cancers, and immune disorders.

BACKGROUND OF THE INVENTION

The presence of viral nucleic acids represents a danger signal for theimmune system which initiates an anti-viral response to impede viralreplication and eliminate the invading pathogen¹. Interferon (IFN)response is a major component of the anti-viral response and comprisesthe production of type I IFNs, IFN-α and IFN-β. An anti-viral responsealso comprises the production of various other cytokines, such as IL-12,which promote innate and adaptive immunity¹.

In order to detect foreign nucleic acids, immune cells are equipped witha set of pattern recognition receptors (PRR) which act at the frontlineof the recognition process and which can be grouped into two majorclasses: the Toll-like receptors and the RNA helicases.

Members of the Toll-like receptor (TLR) family have been implicated inthe detection of long dsRNA (TLR3)², ssRNA (TLR7 and 8)^(3, 4), shortdsRNA (TLR7)⁵ and CpG DNA (TLR9)⁶. The TLRs reside primarily in theendosomal membranes of the immune cells^(7, 8) and recognize viralnucleic acids that have been taken up by the immune cells into theendosomal compartments⁹.

RNA helicases, such as RIG-I, MDA-5 and LGP-2, have been implicated inthe detection of viral RNA^(10, 11). In contrast to the TLRs, the RNAhelicases are cytosolic and are expressed in a wide spectrum of celltypes, including immune cells and non-immune cells, such as fibroblastsand epithelial cells¹². Therefore, not only immune cells, but alsonon-immune cells which express one or more of the RNA helicase(s), arecapable of detecting and responding to viral RNA.

Both the TLR and the RNA helicase systems co-operate to optimally detectviral RNA.

Given the abundance of host RNA present in the cytoplasm, it is anintricate task to specifically and reliably detect virus-derived RNA.Maximal sensitivity together with a high degree of specificity for“non-self” are required. Two major mechanisms appear to be in place invertebrate cells to distinguish “non-self” from “self” nucleic acids viaa protein receptor-based recognition system: (1) the detection of apathogen-specific compartmentalization, and (2) the detection of apathogen-specific molecular signature or motif.

Endosomal RNA is recognized by the TLRs as “non-self”⁴. Notably, hostRNA can acquire the ability to stimulate an IFN response via theactivation of TLRs under certain pathological situations¹³.

Furthermore, there exist structural motifs or molecular signatures thatallow the pattern recognition receptors (PRRs) to determine the originof an RNA. For example, long dsRNA has been proposed to stimulate an IFNresponse via TLR3², RIG-I¹¹ and MDA-5¹⁴. The present inventors recentlyidentified the 5′ triphosphate moiety of viral RNA transcripts as theligand for RIG-I^(15, 19). Even though nascent nuclear endogenous hostRNA transcripts initially also contain a 5′ triphosphate, severalnuclear post-transcriptional modifications, including 5′ capping,endonucleolytic cleavage, and base and backbone modifications, of thenascent RNA transcripts lead to mature cytoplasmic RNAs which areignored by RIG-I. In addition, blunt-ended short dsRNA without any 5′phosphate group¹⁶ or with 5′ monophosphate²⁴ has also been postulated tostimulate RIG-I. A clearly defined molecular signature has not yet beenreported for the ssRNA-sensing TLRs, TLR7 and TLR8. However, the factthat certain sequence motifs are better recognized than others by theTLRs suggests that the nucleotide composition of the RNA, on top ofendosomal localization, may represent basis for discriminating between“self” and “non-self” by the TLRs^(3-5, 10, 11, 17, 18).

Despite its pivotal role in anti-viral defense, the mechanism of viralRNA recognition by RIG-I is not yet fully elucidated. Therefore, thereis a need in the art to better understand the recognition of viraland/or other non-self RNA by RIG-I. Furthermore, given the efficacy ofIFN-α in various clinical applications, there is a need in the art toprovide alternative agents for inducing IFN-α production in vitro and invivo.

It is therefore an object of the present invention to further identifythe structural motifs or molecular signatures of an RNA molecule whichare recognized by RIG-I. It is another object of the present inventionto prepare RNA molecules which are capable of activating RIG-I andinducing an anti-viral, in particular, an IFN, response in cellsexpressing RIG-I. It is a further object of the present invention to usesaid RNA molecules for inducing an anti-viral, in particular, an IFN,response in vitro and in vivo. It is an ultimate object of the presentinvention to use said RNA molecules for preventing and/or treatingdiseases or conditions which would benefit from an anti-viral, inparticular, an IFN, response, such as infections, tumors/cancers, andimmune disorders.

Cellular transformation and progressive tumor growth result from anaccumulation of genetic and epigenetic changes that alter normal cellproliferation and survival pathways³⁸. Tumor pathogenesis is accompaniedby a process called cancer immunoediting, a temporal transition fromimmune-mediated tumor elimination in early phases of tumor developmentto immune escape of established tumors. The interferons (IFNs) haveemerged as central coordinators of these tumor-immune-systeminteractions³⁹. Due to their plasticity tumors tend to evadesingle-targeted therapeutic approaches designed to control proliferationand survival of tumor cells⁴⁰. Tumors even evade immunotherapies thatare directed at multiple tumor antigens⁴¹.

It is therefore a further object of the present invention to use saidRNA molecules for inducing apoptose, or both for inducing an anti-viral,in particular, an IFN, response in vitro and in vivo and for inducingapoptosis in the same molecule.

There remains a need in the art for combinatorial approaches thatsuppress tumor cell survival and at the same time increaseimmunogenicity of tumor cells in order to provide more effective tumortreatments^(42,43).

SUMMARY OF THE INVENTION

The present invention provides an oligonucleotide preparation comprisingan essentially homogenous population of an oligonucleotide,

-   -   wherein the oligonucleotide has at least one blunt end,    -   wherein the oligonucleotide comprises at least 1, preferably at        least 3, more preferably at least 6 ribonucleotide(s) at the 5′        end at the blunt end,    -   wherein the blunt end bears a 5′ triphosphate attached to the        most 5′ ribonucleotide, wherein the 5′ triphosphate is free of        any cap structure,    -   wherein the blunt end is an end of a fully double-stranded        section, and wherein the fully double-stranded section is at        least 19, preferably at least 21, more preferably at least 24        base pairs in length.

In one embodiment, the oligonucleotide is double-stranded.

In another embodiment, the double-stranded section is the stem of asingle-stranded oligonucleotide having a stem-and-loop structure.

In one embodiment, the oligonucleotide comprises at least one inosine.

In another embodiment, the most 5′ ribonucleotide with the triphosphateattached to is selected from A, G and U, preferably A and G, and mostpreferably A.

In a specific embodiment, the sequence of the first 4 ribonucleotides atthe 5′ end is selected from: AAGU, AAAG, AUGG, AUUA, AACG, AUGA, AGUU,AUUG, AACA, AGAA, AGCA, AACU, AUCG, AGGA, AUCA, AUGC, AGUA, AAGC, AACC,AGGU, AAAC, AUGU, ACUG, ACGA, ACAG, AAGG, ACAU, ACGC, AAAU, ACGG, AUUC,AGUG, ACAA, AUCC, AGUC, wherein the sequence is in the 5′->3′ direction.

In yet another embodiment, the oligonucleotide is free of modificationsselected pseudouridine, 2-thiouridine, 2′-Fluorine-dNTP, in particular2′-fluorine-dCTP, 2′-fluorine-dUTP.

In a preferred embodiment, the most 3′ nucleotide which base pairs withthe most 5′ ribonucleotide bearing the 5′ triphosphate at the blunt endis 2′-O-methylated. More preferably, said nucleotide is 2′-O-methylatedUTP.

In a further embodiment, the oligonucleotide comprises at least onestructural motif recognized by at least one of TLR3, TLR7, TLR8 andTLR9.

In an additional embodiment, the oligonucleotide has gene-silencingactivity.

In a preferred embodiment, the oligonucleotide having gene-silencingactivity is a siRNA.

In a further embodiment, the oligonucleotide of the invention has bothgene-silencing activity and the ability of RIG-I activation, e.g. adouble-stranded oligonucleotide with a 5′-triphosphate end (3p-siRNA).

In a further embodiment, the oligonucleotide of the invention hasgene-silencing activity and the ability of RIG-I activation, e.g. adouble-stranded oligonucleotide with a 5′-triphosphate end (3p-siRNA),and contains sequences or structural motifs that are recognized by TLR7and activate TLR7.

The present invention provides a pharmaceutical composition comprisingat least one oligonucleotide preparation of the present invention and apharmaceutically acceptable carrier.

In one embodiment, the pharmaceutical composition further comprises atleast one agent selected from an immunostimulatory agent, an antigen, ananti-viral agent, an anti-bacterial agent, an anti-tumor agent, retinoicacid, IFN-α, and IFN-β.

The present invention further provides the use of at least oneoligonucleotide preparation of the present invention for the preparationof a composition for inducing type I IFN production.

The present invention also provides the use of at least oneoligonucleotide preparation of the present invention for the preparationof a composition for preventing and/or treating a disease or conditionselected from an infection, a tumor, and an immune disorder.

In one embodiment, the oligonucleotide preparation is used incombination with at least one agent selected from an immunostimulatoryagent, an antigen, an anti-viral agent, an anti-bacterial agent, ananti-tumor agent, retinoic acid, IFN-α, and IFN-β.

In another embodiment, the composition is prepared for administration incombination with at least one treatment selected from a prophylacticand/or a therapeutic treatment of an infection, a tumor, and an immunedisorder.

The present invention additionally provides an in vitro method forinducing type I IFN production in a cell, comprising the steps of:

-   -   (a) mixing at least oligonucleotide preparation of the present        invention with a complexation agent; and    -   (b) contacting a cell with the mixture of (a), wherein the cell        expresses RIG-I.

The present invention provides an oligonucleotide preparation comprisingan essentially homogenous population of a single-strand oligonucleotide,wherein the oligonucleotide has a nucleotide sequence which is 100%complementary to at least 19, preferably at least 21 nucleotides at thevery 5′ end of the genomic RNA of a negative single-strand RNA virus.The present invention further provides the use of said oligonucleotidepreparation for the preparation of a composition for preventing and/ortreating an infection by the negative single-strand RNA virus in amammal.

The present invention also provides an oligonucleotide preparationcomprising an essentially homogenous population of a single-strandoligonucleotide, wherein the oligonucleotide has a nucleotide sequencewhich is 100% complementary to the nucleotide sequence at the 5′ end ofthe genomic RNA of a negative single-strand RNA virus betweennucleotides 2+m and 2+m+n, wherein m and n are independently positiveintegers, wherein m equals to or is greater than 1 and is less than orequals to 5, and wherein n equals to or is greater than 12. The presentinvention further provides the use of said oligonucleotide preparationfor the preparation of a composition for preventing and/or inhibiting atype I IFN response against the single-strand RNA virus in a mammal. Thepresent invention additionally provides the use of said oligonucleotidepreparation for the preparation of a composition for treatingvirus-induced hemorrhagic fever.

In certain embodiments, the negative single-strand RNA virus is selectedfrom influenza A virus, Rabies virus, Newcastle disease virus (NDV),vesicular stomatitis virus (VSV), Measles virus, mumps virus,respiratory syncytial virus (RSV), Sendai virus, Ebola virus, orHantavirus.

In a further embodiment, the present invention is directed to anoligonucleotide preparation as defined above having the ability toinduce apoptosis.

In a further embodiment, the present invention is directed to anoligonucleotide preparation as defined above having the ability topreferentially induce apoptosis in tumor cells compared to primarycells, for example if the tumor is a melanoma the primary cells may bemelanocytes or fibroblasts.

In a further embodiment, the present invention is directed to anoligonucleotide preparation as defined above having two distinctfunctional properties: a) gene silencing and b) RIG-I activation.Particularly preferred are anti-bcl-2 double-stranded oligonucleotideswith 5′-triphosphate ends (3p-siRNA). The present invention furtherprovides a pharmaceutical composition comprising said oligonucleotidepreparations having two distinct functional properties and optionally apharmaceutically acceptable carrier. The present invention furtherprovides a pharmaceutical composition comprising said oligonucleotidepreparations having apoptose-inducing activity. The present inventionadditionally provides the use of said oligonucleotide preparationshaving two distinct functional properties for the preparation of apharmaceutical composition for treating cancer, in particular melanomas.

The present invention further provides a pharmaceutical compositioncomprising at least one of the above-described oligonucleotidepreparation and a pharmaceutically acceptable carrier.

The present invention provides a method for preparing a double-strandoligonucleotide preparation having type I IFN-inducing activity,comprising the steps of:

-   (a) identifying two oligonucleotide sequences, wherein at least one    of the nucleotide sequences comprises at least 1 ribonucleotide at    the 5′ end, wherein the sequence of the at least 19, preferably at    least 21 nucleotides at the 5′ end of the at least one    oligonucleotide sequence which comprises at least 1 ribonucleotide    at the 5′ end has 100% complementarity with the sequence of the at    least 19, preferably at least 21 nucleotides at the 3′ end of the    other oligonucleotide sequence, thereby forming a blunt end;-   (b) preparing two essentially homogenous populations of two    oligonucleotides having the sequences identified in (a), wherein the    at least one oligonucleotide which comprises at least 1    ribonucleotide at the 5′ end which forms the blunt end bears a 5′    triphosphate on the most 5′ ribonucleotide;-   (c) preparing an essentially homogenous population of a    double-strand oligonucleotide from the two oligonucleotides prepared    in (b); and-   (d) optionally testing the type I IFN-inducing activity of the    double-strand oligonucleotide.-   The present invention provides a method for preparing a    single-strand oligonucleotide preparation having type I IFN-inducing    activity, comprising the steps of:-   (a) identifying an oligonucleotide sequence, wherein the nucleotide    sequence comprises at least 1 ribonucleotide at the 5′ end, wherein    the sequence of the at least 19, preferably at least 21 nucleotides    at the 5′ end of the oligonucleotide sequence has 100%    complementarily with the sequence of the at least 19, preferably at    least 21 nucleotides at the 3′ end of the oligonucleotide sequence;-   (b) preparing an essentially homogenous population of an    oligonucleotide having the sequence identified in (a), wherein the    oligonucleotide bears a 5′ triphosphate on the most 5′    ribonucleotide; and-   (c) optionally testing the type I IFN-inducing activity of the    single-strand oligonucleotide.-   The present invention provides a method for preparing an    oligonucleotide preparation having the combined activity of target    gene silencing and type I IFN inducing activity, comprising the    steps of:-   (a) identifying an oligonucleotide sequence, wherein the nucleotide    sequence is specific for the target gene and comprises at least 1    ribonucleotide at the 5′ end, wherein the sequence of the at least    19, preferably at least 21 nucleotides at the 5′ end of the    oligonucleotide sequence has 100% complementarity with the sequence    of the at least 19, preferably at least 21 nucleotides at the 3′ end    of the oligonucleotide sequence;-   (b) preparing an essentially homogenous population of an    oligonucleotide having the sequence identified in (a), wherein the    oligonucleotide bears a 5′ triphosphate on the most 5′    ribonucleotide;-   (c) optionally testing the type I IFN-inducing activity of the    single-strand oligonucleotide; and-   (d) optionally testing the oligonucleotide for gene-silencing    activity.-   The present invention further provides a method for preparing an    oligonucleotide preparation having the combined activity of target    gene-silencing and type I IFN-inducing activity, comprising the    steps of:-   (a) identifying a nucleotide sequence for a first oligonucleotide,    wherein the nucleotide sequence is specific for the target gene;-   (b) preparing an essentially homogenous population of the first    oligonucleotide having the sequence identified in (a),-   (c) preparing a essentially homogenous population of a second    oligonucleotide wherein the nucleotide sequence of the second    oligonucleotide is 100% complementary to the nucleotide sequence of    the first oligonucleotide;-   (d) optionally testing the type I IFN-inducing activity of the    single-strand oligonucleotide; and-   (e) optionally testing the oligonucleotide for gene-silencing    activity;    wherein the first and/or the second oligonucleotide bears a 5′    triphosphate on the most 5′ ribonucleotide or on both 5′    ribonucleotides; wherein the 5′ triphosphate is free of any cap    structure; and wherein the first and the second oligonucleotide has    at least 19, preferably at least 21, more preferably at least 24    base pairs in length.

The present invention provides a method for enhancing the type IIFN-inducing activity of an oligonucleotide, wherein the oligonucleotidehas at least one blunt end and comprises at least 1 ribonucleotide atthe 5′ end at the blunt end, wherein the blunt end bears a 5′triphosphate attached to the most 5′ ribonucleotide, wherein the 5′triphosphate is free of any cap structure, and wherein the blunt end isfollowed by a fully double-stranded section which is at least 19,preferably at least 21 base pair (bp) in length, comprising the step of2′-O-methylating the most 3′ nucleotide which base pairs with the most5′ ribonucleotide bearing the 5′ triphosphate at the blunt end.

The present invention also provides a method for reducing the type IIFN-inducing activity of an oligonucleotide, wherein the oligonucleotidehas at least one blunt end and comprises at least 1 ribonucleotide atthe 5′ end at the blunt end, wherein the blunt end bears a 5′triphosphate attached to the most 5′ ribonucleotide, wherein the 5′triphosphate is free of any cap structure, and wherein the blunt end isfollowed by a fully double-stranded section which is at least 19,preferably at least 21 base pair (bp) in length, comprising the step of2′-O-methylating a nucleotide which is not the most 3′ nucleotide whichbase pairs with the most 5′ ribonucleotide bearing the 5′ triphosphateat the blunt end; preferably, the nucleotide to be 2′-O-methylated isthe nucleotide immediately 5′ to the most 3′ nucleotide which base pairswith the most 5′ ribonucleotide bearing the 5′ triphosphate at the bluntend.

The present invention further provides a method of determining whether adouble stranded RNA (dsRNA) silences gene expression in a cell in vivoby an RNA interference (RNAi) mechanism, wherein the dsRNA comprises atleast two sequences that are complementary to each other, and wherein asense strand comprises a first sequence, and an antisense strandcomprises a second sequence, which comprises a region of complementarityto an mRNA expressed in a mammal, wherein the region of complementarityis 19 to 20 nucleotides in length, and wherein the dsRNA furthercomprises a 5′triphosphate, the method comprising:

-   (i) providing an RNA sample isolated from the mammal, wherein the    mammal was previously administered the dsRNA; and-   (ii) performing 5′-rapid amplification of cDNA ends (5′RACE) to    detect the cleavage site of the mRNA in the RNA sample;    wherein if the mRNA detectable by 5′RACE is cleaved at the predicted    site, then the dsRNA is determined to silence gene expression by an    RNAi mechanism.

In one embodiment of the method of determining whether a double strandedRNA (dsRNA) silences gene expression in a cell in vivo, the mRNAexpressed in the mammal is a Bcl-2 mRNA.

In a further embodiment of the above method of determining whether adouble stranded RNA (dsRNA) silences gene expression in a cell in vivo,the mammal is a mouse.

In a further embodiment of the above method of determining whether adouble stranded RNA (dsRNA) silences gene expression in a cell in vivo,the dsRNA was administered intravenously.

In a further embodiment of the above method of determining whether adouble stranded RNA (dsRNA) silences gene expression in a cell in vivo,the dsRNA comprises a 5′triphosphate on the sense strand and theantisense strand of the dsRNA.

In a further embodiment of the above method of determining whether adouble stranded RNA (dsRNA) silences gene expression in a cell in vivo,the predicted cleavage site is at the nucleotide corresponding to thenucleotide ten nucleotides away from the 5′ end of the antisense strandof the dsRNA.

The present invention further provides a method of determining whether adouble stranded RNA (dsRNA) silences gene expression in cells in vitroby an RNA interference (RNAi) mechanism, wherein the dsRNA comprises atleast two sequences that are complementary to each other, and wherein asense strand comprises a first sequence, and an antisense strandcomprises a second sequence, which comprises a region of complementarityto an mRNA expressed in the cells, wherein the region of complementarityis 19 to 20 nucleotides in length, and wherein the dsRNA furthercomprises a 5′triphosphate, the method comprising:

-   (i) providing an RNA sample isolated from the cells, wherein the    cells were previously contacted with the dsRNA; and-   (ii) performing 5′-rapid amplification of cDNA ends (5′RACE) to    detect the cleavage site of the mRNA in the RNA sample;    wherein if the mRNA detectable by 5′RACE is cleaved at the predicted    site, then the dsRNA is determined to silence gene expression by an    RNAi mechanism.

In one embodiment of the method of determining whether a double strandedRNA (dsRNA) silences gene expression in cells in vitro, the mRNAexpressed in the mammal is a Bcl-2 mRNA.

In a further embodiment of the above method of determining whether adouble stranded RNA (dsRNA) silences gene expression in cells in vitro,the cells are B 16 melanoma cells.

In a further embodiment of the above method of determining whether adouble stranded RNA (dsRNA) silences gene expression in cells in vitro,the dsRNA comprises a 5′triphosphate on the sense strand and theantisense strand of the dsRNA.

In a further embodiment of the above method of determining whether adouble stranded RNA (dsRNA) silences gene expression in cells in vitro,the predicted cleavage site is at the nucleotide corresponding to thenucleotide ten nucleotides away from the 5′ end of the antisense strandof the dsRNA.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. Recognition of 3pRNA occurs through differential pathways inmonocytes and PDCs. (A) Monocytes and PDCs were pre-incubated with 1000ng/ml chloroquine (white bars) or left untreated (black bars). After 30min cells were stimulated with 3pRNA GA or 3pRNA GFPs complexed withlipofectamine (as indicated) or control (no nucleic acid). Supernatantswere collected 20 h post stimulation and IFN-α production was determinedby ELISA. The results are representative for two experiments andmean±SEM is shown. (B) Sorted PDCs from Flt3-L-induced bone marrowcultures of wild-type (WT; black bars) and TLR7-deficient mice(TLR7^(−/−); white bars) were transfected with 200 ng of SynRNA, 3pRNAand CpG ODN2216 (3 μg/ml). After 24 h, IFN-α production was determinedby ELISA. Data are expressed as the mean±SEM of two independentexperiments.

FIG. 2. Blunt end synthetic dsRNA is a poor inducer of IFN-α inmonocytes. (A-B) Synthetic ssRNA and dsRNA with (27+2) or without (27+0)2-nt overhangs were transfected into PDCs and monocytes in complex withlipofectamine 2000. CpG ODN 2216 (3 μg/ml) and 3pRNA GFPs (200 ng) wereused as a positive control stimulus for TLR and RIG-I, respectively. Thelevels of IFN-α production were analyzed by ELISA 24 h after stimulationand are depicted as mean±SEM of two independent experiments.

FIG. 3. Experimental design: synthetic RNA oligonucleotides used to testthe effect of end structure on the immunostimulatory activity ofdouble-stranded 3pRNA.

FIGS. 4-6. Blunt end at the end bearing the 5′ triphosphate augments theimmunostimulatory activity of synthetic double-stranded 3pRNAoligonucleotides. Purified monocytes, PDC-depleted PBMCs and PBMCspre-treated with chloroquine were transfected with the indicatedsingle-stranded or double-stranded synthetic RNA oligonucleotide. IFN-αproduction was analyzed 24 hours after stimulation. Data from three orfour independent donors were summarized and are depicted as meanvalues±SEM.

FIG. 7. Single-stranded RNA oligonucleotide can be obtained by in vitrotranscription. (A) In vitro transcribed, synthetic or mixeddouble-stranded or single-stranded oligonucleotides were transfectedinto purified monocytes. IFN-α production was analyzed 24 hours afterstimulation. (B) Urea polyacrylamide gel electrophoresis. (C) Sequenceof the oligonucleotides tested.

FIG. 8. The effect of 2′-O-methylation on the IFN-α-inducing activity ofa blunt ended RNA olignucleotide bearing 5′ triphosphate isposition-dependent. Purified monocytes were stimulated with 0.8 μg/ml ofthe indicated double-stranded oligonucleotides. IFN-α production wasanalyzed 24 hours after stimulation. Data from six independent donorswere summarized and are depicted as mean values±SEM.

FIG. 9. Fully synthetic 5′triphosphate single strand RNA is notsufficient to activate RIG-I. (A) Reverse Phase HPLC analysis of3P-A=pppAAC ACA CAC ACA CAC ACA CAC UUU (1) after deprotection understandard ACE deprotection conditions (pH=3.8, 60° C. in 30 min). (B)MALDI-ToF analysis of 3P-A: calculated molecular weight of 3P-A is 7770;the peak at 3886 represents the double charged anion peak (z=2). (C)MALDI-ToF analysis of 3P-A mixed with HO-A. The difference between themolecular weight of the product 3P-A (1) and the educt HO-A (2) is 240which corresponds to the molecular weight of an additional triphosphategroup (H₃P₃O₉). (D) Purified monocytes were stimulated with theindicated single strand or double strand synthetic or in vitrotranscribed RNA oligonucleotide. The question mark indicates that the3′end of this in vitro transcribed RNA is not molecularly defined. IFN-αproduction was analysed 24 hours after stimulation. Data from fourindependent donors are depicted as mean values±SEM. (E) Indicated RNAstimuli (see Table 5) were analysed on a denaturing 12% polyacrylamidegel (containing 50% urea w/v) and stained with methylene blue detectingsingle strand and double strand RNA. Ivt3P-G w/o U was generated by invitro transcription in the absence of the nucleotide UTP. (F) Monocyteswere stimulated with single and double strand RNA as indicated. RNAswere analysed on a denaturing 12% polyacrylamide gel (containing 50%urea w/v) and stained with methylene blue.

FIG. 10. RIG-I activation requires a short double strand of at least 21base pairs and prefers 5′-adenine. Purified monocytes were stimulatedwith the indicated single strand or double strand synthetic RNAoligonucleotide. IFN-α production was analysed 24 hours afterstimulation. Data from three or four (NC), eight (B) or twelve (C)independent donors are depicted as mean values±SEM. (A) 3P-A washybridized with synthetic antisense single strand RNA with differentlengths generating double strand RNA with blunt end carrying thetriphosphate group. (B) 23mer (AS G23 and AS A23) with a blunttriphosphate end and a 3′overhang at the non-triphosphate end. (C)Comparison of RIG-I ligand activity of 3P-G to the other three syntheticvariants (3P-A, 3P-C, 3P-U) which were hybridized with the correspondingsynthetic 24mer (AS-A24, AS-C24, AS-U24) or used as single strands. (D)IFN-α inducing activity of 3P-A+AS A24 and 3P-G+AS G24.

FIG. 11. Blunt end at the triphosphate end but not at thenon-triphosphate end contributes to RIG-I ligand activity, and5′monophosphate does not substitute for 5′triphosphate. Purifiedmonocytes were stimulated with the indicated single strand or doublestrand synthetic RNA oligonucleotides. IFN-α production was analysed 24hours after stimulation. Data from four independent donors are depictedas mean values±SEM. 3P-G and 3P-A were hybridized with correspondingantisense strands with different lengths and positions. (A) The use of25mer (AS G24+A and AS A24+A) and 26mer (AS G24+2A and AS A24+2A)results in a mononucleotide or dinucleotide 5′ overhang at thenon-triphosphorylated end. (B) The use of 25mer (AS G25 and AS A25) and26mer (AS G26 and AS A26) results in a mononucleotide or dinucleotide 3′overhang at the triphosphate end. (C) The use of 19mer, 21mer and 23mersingle strand antisense RNA (AS19, AS21, AS23) results in a 5′overhangat the triphosphate end (−5 nt, −3 nt, −1 nt). (D) IFN-α-inducingactivity of 5′monophosphate single strand RNA (P-A) and synthetic5′triphosphate single strand RNA (3P-A) and combinations withcomplementary strands of different lengths are compared.

FIG. 12. IFN-α inducing activity of RIG-I RNA ligands correlates withRIG-I ATPase activity and with RIG-I binding affinity. (A) For theATPase assay purified RIG-I protein was incubated with increasingamounts of indicated RNA molecules (from 10⁻⁹ nM to 1800 nM) and therelease of ADP was analysed after 30 min at 37° C. by a FRET-basedcompetitive immunoassay. The percentage of ADP release is plottedagainst the decadic logarithm of the concentration of indicated RNAs.Half effective concentration (EC50) was determined by statisticalanalysis (non-linear regression). Low EC50 represents high RIG-I ATPaseactivity. (B) The EC50 of the synthetic 3P-A hybridized with theindicated antisense RNAs are compared. (C) The EC50 of 5′triphosphatedouble strand RNA with different 5′bases (A, G, U, C) are compared. (D)Purified (His6)-tagged RIG-I was incubated with different RNA moleculesbearing a biotin on the 5′end of the antisense strand (at thenon-triphosphate end of the double strand RNA). (His6)-tagged RIG-Iprotein was bound to Ni-chelate beads (donor); biotinylated RNA wasbound to streptavidine beads (acceptor). The resulting fluorescencecorrelates with the number and proximity of interacting donor-acceptorpairs. Concentration of indicated RNAs is plotted against the percentageof maximum binding to RIG-I. The dissociation constant Kd(app) iscalculated by statistical analysis (non-linear regression). (E) and (F)Kd(app) of non-modified, monophosphate and triphosphate RNAs hybridizedto indicated antisense RNAs of different lengths are compared. (F) CIAP3P-A+AS A24 was incubated with active alkaline phosphatase; the otherstimuli were incubated with heat-inactivated active alkalinephosphatase. (G) Purified (His6)-tagged RIG-I protein was analysed bySDS-PAGE and Coomassie Blue staining.

FIG. 13. Length and 5′ and 3′overhang impact on IFN-a stimulatingactivity of short double strand RNA. Purified monocytes were stimulatedwith the indicated single strand or double strand synthetic RNAoligonucleotides. IFN-a production was analyzed 24 hours afterstimulation. (A) 3P-G and 3P-A hybridized with antisense strands ofdifferent lengths and binding positions are compared. (B) 3P-Ahybridized with an antisense strand resulting in a double strand RNAwith a 10 base long 3 overhang at the triphosphate end.

FIG. 14. Confirmation of structural requirements for RIG-I activationusing an independent RNA sequence (GFP). Purified monocytes werestimulated with the indicated single strand or double strand syntheticRNA oligonucleotides (3P-GFP1, and variations thereof). IFN-a productionwas analyzed 24 hours after stimulation.

FIG. 15. 5′- and 3′monophosphate double strand RNA is not sufficient forIFN-a induction in human monocytes. Purified monocytes were stimulatedfor 24 hours with the indicated single-stranded or double-strandedsynthetic RNA oligonucleotide, and IFN-a was analysed in thesupernatants. Sequences are from Takahasi and colleagues²⁴.

FIG. 16. Panhandle configuration of negative strand RNA viruses. Insilico hybridizations³ of the 5′ and the 3′ end of different negativestrand RNA viruses. The 5′ nucleoside is adenosin.

FIG. 17. 3p-2.2 siRNA potently silences Bcl-2 expression and reducesmetastatic growth of B16 melanoma cells in the lungs.

(a) Left panel: Western blot analysis of Bcl-2 protein expression in B16cells 48 h after transfection with the chemically synthesized siRNAsanti-Bcl-2 2.1, anti-Bcl-2 2.2 and anti-Bcl-2 2.3. A non-silencing siRNA(control RNA=Ctrl.) served as negative control. Right panel: Westernblot analysis of Bcl-2 protein expression in B16 cells 48 h aftertransfection with the indicated in vitro transcribed anti-Bcl-23p-siRNA-2.2 (3p-2.2) The 3p-siRNAs 3p-GC and mismatch 3p-MM served asnegative controls. One representative experiment of four is shown. (b)Left panel: In vitro 5′-RACE analysis of RNA extracted from B16 cells 2h after treatment with the indicated RNAs. Black arrows mark the5′-RACE-PCR amplification product showing the predicted product ofRNA-interference (334 nt expected size). Right panel: schematic diagramshowing the position of the predicted siBcl-2 cleavage site relative tonested primers used for PCR amplification of the cleavage fragment. (c)Intravenous challenge of C57BL/6 mice with B16 melanoma cells andtreatment with 50 μg of the indicated siRNAs intravenously on days 3, 6,and 9. The mean number of macroscopically visible melanoma metastases onthe lung surfaces of each group (±SEM) are shown after 12 (left panel)or 17 days (right panel) are shown. (P*<0.05 or P**<0.01; Mann-Whitney Utest).

FIG. 18. Activation of type I IFNs and NK cells are necessary for theanti-tumor activity of Bcl-2-specific immunostimulatory 3p-siRNA in vivo

(a) Intravenous challenge of wild-type (WT), IFN-α-receptor 1-deficient(IFNAR^(−/−)) or toll-like receptor 7-deficient (TLR^(−/−)) C57BL/6 micewith B16 melanoma cells and treatment with 50 μg of the indicated siRNAsintravenously on days 3, 6, and 9. The mean number of macroscopicallyvisible melanoma metastases on the lung surfaces of each group (±SEM)are shown. Left panel: P*<0.05 between 3p-2.2 and control RNA-treated inWT mice; n=4; Mann-Whitney U test; Middle panel: P*>0.05 between 3p-2.2and control RNA-treated IFNAR^(−/−) mice (n=4); Right panel: P*<0.05between 3p-2.2 and control RNA-treated TLR7^(−/−) mice (n=4) (b) Effectof antibody-based depletion of CD8 T cells (anti-mCD8), NK cells(anti-TMβ1) or control antibody (anti-Rat-IgG) on the therapeuticanti-tumor efficacy of 3p-2.2 in C57BL/6 wildtype mice (P*<0.05; n=5).

FIG. 19. Bcl-2-specific immunostimulatory 3p-siRNA induces cell-typespecific innate immune responses and apoptosis in vitro

(a) Levels of IFN-α in the culture supernatant of conventional dendriticcells (cDC) measured by ELISA 24 h after transfection with the indicatedRNAs. Data are shown as means±SEM of two independent experiments. (b)Flow cytometric analysis of apoptosis induction in cultured cDCs andfreshly isolated B cells, T cells, NK cells and whole spleen cells 48 hafter transfection with the indicated RNAs. Results are shown asmean±SEM of two independent experiments. (c) Analysis of IFN-β promoteractivation in B16 cells 24 h after transfection with the indicated RNAs.Results of luciferase measurements are shown as mean±SEM. (d) Westernblot analysis of RIG-I expression in B16 cells 8 h after treatment with3p-2.2 (1 μg/ml) or murine IFN-β (1,000 U ml⁻¹). HEK293 cellsoverexpressing RIG-I served as positive control. (e) Flow cytometricanalysis of apoptosis induction in B16 cells 48 h after transfectionwith the indicated RNAs. Results are shown as mean±SEM of fourindependent experiments (P*<0.05; t-test) (f) Flow cytometric analysisof apoptosis induction in B16 cells 48 h after cotransfection with theindicated RNAs in combination with siRNA for IFNAR or RIG-I. Data areshown as mean±SEM of three independent experiments (P*<0.05; t-test).(g) Flow cytometric analysis of apoptosis induction in primary murineembryonal fibroblasts (MEFs) and immortalized murine fibroblasts(NIH-3T3) treated as indicated. Exposure to staurosporine served as apositive control.

FIG. 20. Bcl-2-specific gene silencing and activation of the innateimmune system synergistically promotes tumor cell apoptosis in vivo

(a) Serum IFN-α levels in mice measured by ELISA 6 h after injection oftumor-bearing mice with the indicated siRNAs. Data are shown as mean±SEMof four mice per group. (b) Flow cytometric analysis of NK cells insingle cell suspensions of metastatic lungs. Results are presented asmean numbers of NK-1.1 positive cells±SEM (P*<0.05 between 3p-2.2 andcontrol RNA-treated mice; P*<0.05 between 3p-GC and control RNA-treatedmice; n=4). (c) Flow cytometric analysis of NK cell activation in singlecell suspensions of metastatic lungs. Results are presented as meanpercentage of CD69+ of NK1.1+ cells±SEM (P*<0.05 between OH-2.2 andcontrol RNA-treated mice; P**<0.01 between 3p-2.2, 3p-GC and control RNAtreated mice; n=4; t-test). (d) Quantification of Bcl-2 proteinexpression in HMB45+ B16 tumor cells derived from single cellsuspensions of metastatic lungs. Depicted is the mean fluorescenceintensity (MFI)±SEM (P*<0.05 between 3p-2.2 and 3p-GC-treated mice;P*<0.05 between OH-2.2 and control RNA-treated mice; n=4; t-test). (e)In vivo 5′-RACE analysis of RNA extracted from metastatic lungs. (f)Upper panel: Immunohistochemical visualization of melanoma cells in lungtissue sections of tumor-bearing mice (black arrows). Lower panel:Detection of apoptotic cells within metastases by TUNEL staining (blackarrows). Representative sections of one experiment with five mice/groupare shown.

FIG. 21. Bcl-2-specific gene silencing contributes to 3p-siRNA inducedinhibition of tumor growth and apoptosis

(a) Western blot analysis of Bcl-2 protein expression in B16 cellsstably transfected with wilde-type Bcl-2 (WT-B16) or a specificallymutated Bcl-2 cDNA (Mut-B16) after treatment with the indicated siRNAs.(b) Left panel: Flow cytometric analysis of apoptosis induction inWT-B16 or Mut-B16 cells 48 h after transfection with the indicated RNAs.Results are shown as mean percent of apoptotic cells±SEM of threeindependent experiments. Right panel: one representative dot plot ofthree independent experiments is shown. (c) Intravenous challenge ofC57BL/6 mice with B16 melanoma cells and treatment with the indicatedsiRNAs. The mean number of macroscopically visible melanoma metastaseson the lung surfaces of each group (±SEM) are shown. (d) Serum IFN-αlevels 6 h after treatment of tumor-bearing mice with the indicated RNA.Data are shown as mean±SEM of four mice/group (e) Intravenous challengeof C57BL/6 mice with WT-B16 or Mut-B16 melanoma cells and treatment withthe indicated siRNAs. The mean number of macroscopically visiblemelanoma metastases on the lung surfaces of each group (±SEM) are shown.*P<0.01, Mann-Whitney U test).

FIG. 22. Bcl-2-specific 3p-siRNA is effective in other models oftumorigenesis and in human melanoma

(a) Left panel: Treatment of CDK4^(R24C) mice with transplantedHGF×CDK4^(R24C) melanomas in the skin by intra- and peritumoralinjections of 3p-2.2 or jetPEI on days 10, 16, 24 and 30. Shown is themean tumor volume of each group in mm³±SEM (**P<0.01). Right panel:Analysis of tumor lysates from transplanted HGF×CDK4^(R24C) melanomasfor Bcl-2, Bim, Mcl-1, Puma and Bcl-xL protein expression by Westernblot 24 h after treatment. (b) Left panel: Treatment of Balb/c mice withC26 tumors in the skin by intravenous injections with the indicatedsiRNAs on days 6, 9, 12 and 15. Shown is the mean tumor area in mm²±SEMof each group (** P<0.01). Right panel: Analysis of Bcl-2 proteinexpression 48 hours after transfection of C26 cells with the indicatedRNAs. (c) Activation of IFN-β RNA expression following treatment of1205Lu cells with the indicated siRNAs using quantitative RT-PCR. Themean±SD of three independent experiments is shown. (d). Left panel: Flowcytometric analysis of apoptosis induction in 1205Lu cells treated withthe siRNAs as described in (c). The mean±SD of three independentexperiments is shown. Right panel: Assessment of Bcl-2-silencingactivity by immunoblotting. Representative results of three independentexperiments are depicted. (e) Cell viability of 1205Lu (threeindependent experiments mean±SD), of human primary melanocytes and humanprimary fibroblasts (both isolated from three different donors,means±SD) 24 h after transfection of 3p-h2.2.

FIG. 23. Gene-silencing of Bcl-2 by 5′-triphosphate siRNA is specific

B16 cells were seeded in 24-well plates at a confluency of 50%, B16cells were transfected with the selected siRNAs at 1 μg/ml. 48 hoursafter transfection, protein expression of mouse Bcl-2, Mcl-1, Puma,Bcl-xL, Bim and β-actin was analysed by Western blot. One representativeout of three independent experiments is shown.

FIG. 24. Gene-silencing of Bcl-2 and IFN-α production by 5′-triphosphatesiRNA is cell-type specific and requires RIG-I, but not MDA-5 or TLR7.

(a) GMCSF-derived cDCs as well as splenocytes, B cells, NK cells and Tcells were transfected with the indicated siRNAs (1 μg/ml). After 24 hIFN-α production was quantified in the supernatant by ELISA. Data areshown as means±SEM of two independent experiments. (b) GMCSF-derived cDCof wild-type (WT), RIG-I- and MDA 5-deficient mice were transfected with1 μg/ml of OH-2.2, 3p-GC, 3p-2.2, and Poly(I:C). After 24 h IFN-αproduction was quantified in the supernatant by ELISA. Data are shown asmeans±SEM of two independent experiments. (c) GMCSF-derived cDC of WTand TLR7-deficient mice were transfected with 1 μg/ml of OH-2.2, 3p-2.2and CpG 2216 (3 μg/ml). After 24 h IFN-α production was quantified inthe supernatant by ELISA. Data are expressed as the mean±SEM of twoindependent experiments. (d) GMCSF-derived cDCs as well as splenocytes,B cells, NK cells and T cells were transfected with the indicated siRNAs(1 μg/ml). After 48 h Bcl-2 expression was analysed by Western blot. Onerepresentative Western blot out of two independent experiments is shown.

FIG. 25. 5′-triphosphate siRNA leads to RIG-1-dependent activation ofB16 cells

(a) B16 cells were treated with the indicated RNAs as described. IP-10production was quantified in the supernatant by ELISA. Data are shown asmeans±SEM of two independent experiments. (b) B16 cells were treatedwith the indicated stimuli as described. After 24 h the number of MHC-Ipositive cells was determined by FACS-analysis. One representativehistogramm out of two independent experiments is shown. (c) B16 cellswere transfected with a control siRNA or RIG-I siRNA at 1 μg/ml. 48 hafter transfection protein expression of RIG-I was analysed by Westernblot. (d) Left panel: B16 cells were co-transfected with control siRNAor RIG-I siRNA and an IFN-β promoter reporter construct drivingluciferase. 24 h after transfection cells were stimulated with 3p-2.2 (1μg/ml). 16 h after stimulation cells were analysed for IFN-β luciferasereporter activity. Data are shown as means±SEM of three independentexperiments. Right panel: B16 cells were transfected with NS3-4A(encoding for a multifunctional serine protease of hepatitis C virusspecifically cleaving and thereby inactivating two adaptor proteins,Cardif and Trif) or the inactive form NS3-4A*. 24 h after transfectionB16 cells were stimulated with 3p-2.2 (1 μg/ml). 16 h after stimulationcells were analysed for IFN-β luciferase reporter activity. Data areshown as means±SEM of two independent experiments; P<0.05 (e) B16 cellswere transfected with a control siRNA or IFNAR siRNA at 1 μg/ml. 24 hafter siRNA transfection B16 cells were stimulated with 3p-2.2 (1 μg/ml)and 48 h after stimulation mRNA expression of IFNAR was analysed byquantitative RT-PCR. mRNA expression values were normalized toHypoxanthine-phosphoribosyl-transferase (HPRT). Data are representativeof two independent experiments.

FIG. 26. 5′-triphosphate siRNA induced IFN-α secretion in vivo dependson the 5′-triphosphate end and on CD11c+ cell subsets, but isindependent of TLR7

(a) C57BL/6 were administered with 50 μg of the indicated siRNAs. After6 h mice were sacrificed and serum was analysed for IFN-α secretion.Data are shown as means±SEM of two independent experiments. (b)CD11c-DTR transgenic mice were injected i.p. with 100 ng DT or PBS (day0). 24 h after injection mice were administered with 50 μg of 3p-2.2 orjetPEI. After 6 h mice were sacrificed and serum was analysed for IFN-α.Data are shown as means+/−SEM of two mice per group and arerepresentative of two independent experiments. (c-e) C57BL/6 and TLR7−/−mice were treated as described in Material and Methods. After 6 h micewere sacrificed and serum was analysed for IFN-α (c), IL-12p40 (d) andIFN-γ (e) by ELISA. Data are shown as means±SEM of three independentexperiments.

FIG. 27. 5′-triphosphate siRNA enhances the production of serumcytokines in vivo

C57BL/6 mice were injected intravenously with increasing doses of 3p-2.2(25, 50 or 75 μg/mouse). Serum was collected after 6 h. Cytokine levelsof IFN-α (a) and IL-12p40 and IFN-γ (b) were determined by ELISA. (c)C57BL/6 mice were injected with 3p-2.2 and OH-2.2 and serum wascollected 12 h, 24 h, and 48 h after injection. Serum cytokine levels ofIFN-α were determined by ELISA. Data are shown as means±SEM of twoindependent experiments. (d-f) C57BL/6 mice were treated with 3p-2.2 andOH-2.2 and blood was collected after 48 h and processed as EDTA plasmafor measurement of (d) leucocytes (WBC), platelets (PLT) (e) anderythrocytes (RBC) (f). Data are shown as means±SEM of two independentexperiments.

FIG. 28. 5′-triphosphate siRNA activates immune cell subsets in vivo

C57BL/6 mice were injected with increasing doses of 3p-2.2 (25, 50 or 75μg/mouse). Left panel: Spleen cells were isolated 48 h after injectionand CD86 or CD69 expression was analysed on PDCs, MDCs, NK cells, CD4 Tcells and CD8 T cells by flow cytometry. Data are shown as means±SEM oftwo independent experiments. Right panel: Histograms of onerepresentative experiment after stimulation with 50 μg 3p-2.2 is shown(grey bar, PBS treated control mice; white bar, 3p-2.2 treated mice).

FIG. 29. 5′-triphosphate siRNA induces NK cell cytotoxicity independentof TLR7

(a) Activation of splenic NK cells isolated from 3p-2.2-injected micestrictly depends on IFNAR, but not on TLR7. Wild-type (WT), TLR7- orIFNAR-deficient mice were injected with 3p-2.2 or PBS as described.After 16 h, splenic NK cells were isolated with DX5 (anti-CD49b)microbeads and assayed for activation (CD69) by flow cytometry. (b) WTor TLR7-deficient mice were injected with OH-2.2, 3p-2.2 or PBS asdescribed. After 16 h, NK cells were isolated from spleens using DX5(anti-CD49b) microbeads and NK cytotoxicity against B16 cells wasmeasured by 51Cr release assay. YAC-1 cytotoxicity of splenic NK cellswas tested at the same time since YAC-1 cells are known to be targetsfor NK cells.

FIG. 30. Uptake of FITC-labeled siRNA in lung metastases and fate ofimmune cell subsets in vivo after 5′-triphosphate siRNA administration.

(a) B16 cells were intravenously injected into C57BL/6 mice and 14 daysafter tumor inoculation, a single dose of FITC-labeled siRNA (100 μg)was administered intravenously. After 6 h the mice were sacrificed andvarious tissues including lungs were excised and the uptake ofFITC-labeled siRNA was analysed by confocal microscopy. Onerepresentative out of two independent experiments after injection with100 μg FITC-labeled siRNA is shown. (b) Total RNA was extracted frommetastatic lungs treated with the indicated RNAs for 24 h and analysedby quantitative RT-PCR for expression of Bcl-2 and Mcl-1. Relative geneexpression was expressed as a ratio of the expression level of the geneof interest to that of hypoxanthine-phosphoribosyl-transferase (HPRT)RNA determined in the same sample. Data are presented as means+/−SD outof two mice/group. (c) C57BL/6 mice were administered with 50 μg of theindicated siRNAs. 24 h after injection spleens were excised and immunecell subsets were analysed for gene-silencing (left panel) and apoptosis(right panel) by flow cytometry. Means+/−SEM out of two independentexperiments are depicted.

FIG. 31. Insertion of two mismatches in the binding site of anti-Bcl-2siRNA

For rescue experiments two central silent mutations (C610A and A612G atamino acid (AA) position 204) were introduced in the target site of2.2-siRNA against murine bcl-2 and subsequently sequenced forconfirmation (data not shown). cDNA encoding wild-type murine bcl-2served as template. CTATATGGCCCCAGCATGAGGCCTCTGTTTGATTTCTCC was used asforward primer (mBcl-2 forward). The central mismatches between theanti-bcl-2 siRNA and the bcl-2 target site result in disrupted basepairing and therefore in the loss of function of the synthetic (OH-2.2)and the 5′-triphosphate siRNA (3p-2.2).

FIG. 32. 5′-triphosphate siRNA leads to RIG-I-dependent apoptosis andactivation of C26 cells

(a) Groups of four tumor-bearing Balb/c mice were injected with controlRNA (Ctrl.), OH-2.2, 3p-GC or 3p-2.2 (50 μg/Mouse) as described. Serawere collected after 6 h and IFN-α levels determined by ELISA. Data areshown as mean+/−SEM of four mice/group. (b) C26 cells were treated withthe indicated stimuli as described. After 24 h the number of Annexin-Vpositive cells was determined by FACS-analysis. Data are presented asmeans+/−SEM out of two independent experiments. (c) C26 cells weretransfected with an IFN-β promoter reporter construct drivingluciferase. 24 h after transfection cells were stimulated with theindicated siRNAs (1 μg/ml). 24 h after stimulation cells were analysedfor IFN-β luciferase reporter activity. Data are shown as means±SEM ofthree independent experiments.

FIG. 33: Schematic diagram of the potential anti-tumor mechanismelicited by 3p-siRNA 3p-2.2 contains two clearly distinct functionalproperties, a) gene silencing and b) RIG-I activation. 3p-2.2 is able totrigger the following distinct anti-tumor mechanism: i) RIG-I isexpressed in immune cells including tumor cells; activation of RIG-Ileads to direct (1) and indirect activation (2) of immune cell subsets(NK cells, CD8 and CD4 T cells) but also provokes innate responsesdirectly in tumor cells (type I IFNs and chemokines) (3). ii) Inaddition RIG-I activation directly induces apoptosis in melanoma cells(which are sensitive to RIG-I mediated apoptosis) (4) and iii) silencingof bcl-2 induces apoptosis in cells that depend on bcl-2 overexpression(5). The activation of RIG-I in tumor cells may synthesize these cellsfor specific destruction by innate effector cells (6).

DETAILED DESCRIPTION OF THE INVENTION

Initially, it was reported that in vitro transcribed siRNAs(small-interfering RNA) which bear 5′ triphosphate, but not syntheticsiRNAs which bear 5′ OH, stimulated the production of type I IFN fromselected cell lines^(20, 21). However, the molecular mechanism which ledto the induction of type I IFN was not known.

Subsequently, it was reported that in vitro transcribed long dsRNA(equal or longer than 50 bp) was detected by RIG-I¹⁰.

Almost at the same time, it was reported that synthetic blunt-endedshort dsRNAs 21-27 bp in length and without any 5′ phosphate group wereligands for RIG-I¹⁶. Furthermore, it was reported that 2-nucleotide 3′overhangs, and to a lesser extend, 5′ overhangs, inactivated RIG-I¹⁶. Itwas postulated that blunt end was the molecular signature recognized byRIG-I

Shortly thereafter, in vitro transcribed short ssRNA and dsRNA bearing5′ triphosphate were identified as the ligands for RIG-I^(15, 19).Furthermore, it was shown that in vitro transcribed short dsRNAs havingthe same sequences as those used in Marques T J et al. (2006)¹⁶stimulated IFN-α production in purified primary human monocytes to thesame degree, regardless whether the dsRNA had blunt ends or 3′overhangs¹⁵. In other words, in the presence of 5′ triphosphate, the endstructure of a dsRNA oligonucleotide did not affect the IFN-α-inducingactivity of the oligonucleotide; the presence of 3′ overhangs did notinactivate RIG-I. This finding confirms the notion that 5′ triphosphateis a molecular signature recognized by and activates RIG-I^(15, 19) andsuggests that blunt end is not a molecular signature that activatesRIG-I¹⁶.

At the same time, it was reported that single-stranded genomic RNA frominfluenza A which bears 5′ phosphates was recognized by RIG-I²⁵.

More recently, it was reported that the C-terminal regulatory domain RDof RIG-I was responsible for the recognition of the 5′ triphosphate onin vitro transcribed ssRNA ligands²⁶.

Almost at the same time, it was reported that dsRNA 25-nucleotide longwith a 5′ monophosphate was also a ligand for RIG-I²⁴. Furthermore,ssRNA bearing 5′ triphosphate was confirmed to be a ligand for RIG-I²⁴.Moreover, it was reported that a blunt-ended dsRNA bearing a 5′monophosphate was more potent at inducing an IFN response than thathaving 3′ overhangs²⁴. However, counter intuitively, it was alsoreported that 5′ monophosphate in dsRNA was not required for interactionwith the C-terminal domain of RIG-I whereas 5′ triphosphate did interactwith the C-terminal domain. In addition, it was reported that theability of a dsRNA oligonucleotide to induce an IFN response wasinversely correlated with the unwinding activity by the helicase domain,which contradicts earlier report that blunt end was not only requiredfor the induction of an IFN response, but also for helicase activity¹⁶.

Also very recently, it was reported that the presence of 2 or 3 G's atthe 5′ end of shRNAs generated by in vitro transcription obliterated theability of the 5′ triphosphate-bearing RNA to induce IFN-β productionvia the RIG-I pathway³⁰. Notably, the shRNAs bearing two 5′ G's, whichhad two G-U wobble base pairs at the end, i.e., a blunt end, werecompletely inactive in inducing an IFN response.

In summary, a number of structurally different RNA molecules have beenreported to be the ligand for RIG-I and different molecular signatureshave been postulated to be recognized by RIG-I. The data in the priorart were inconsistent and at times conflicting with regard to themolecular signatures that were important for activating RIG-I. In otherwords, there was no consensus in the prior art with regard to thecritical molecular signature(s) for RIG-I recognition and activation.

Even though various immune cell types, such as monocytes, plasmacytoiddendritric cells (PDCs), and myeloid dendritic cells (MDCs), are capableof producing IFN-α in response to stimulation by double-stranded RNAoligonucleotides bearing 5′ triphosphate (hereinafter, “3pRNA”;unpublished data from the present inventors), the recognition of suchdouble-stranded 3pRNA oligonucleotides appears to be mediated bydifferent receptors in different cell types. Whereas PDCs appear toutilize TLR7 primarily, monocytes appear to utilize RIG-I primarily(Example 1; FIG. 1). In fact, PDC is the only cell type that produces asignificant amount of IFN-α upon stimulation with an appropriate TLRligand. In contrast, other immune cells, such as myeloid cells, producecytokines other than IFN-α in response to stimulation by TLR ligands.Therefore, monocytes (without contaminating functional PDCs) are idealfor studying the mechanism of ligand recognition by and the activationof RIG-I, with IFN-α production as the readout.

The present inventors stimulated purified primary human monocytes withthe same synthetic blunt-ended short dsRNA without any 5′ phosphate asthat used in Marques T J et al. (2006)¹⁶, and found surprisingly thatthere was no IFN-α production (Example 2; FIG. 2, sample “27+0 ds”).Furthermore, the present inventors stimulated purified primary humanmonocytes with a synthetic blunt-ended short dsRNA bearing a 5′phosphate similar to that used in Takahasi et al. (2008)²⁴, and foundsurprisingly that there was little or no IFN-α production (Example 3;FIG. 6, samples with “P-A” in the name). Theses findings contradictsuggestions in the prior art that blunt-end was a molecular signaturerecognized by RIG-I and was capable of activating RIG-I in the absenceof 5′ triphosphate^(16, 24).

However, very surprisingly, when the present inventors stimulatedpurified primary human monocytes with synthetic dsRNA oligonucleotidesbearing a 5′ triphosphate, they found that the IFN-inducing activity ofthe dsRNA oligonucleotides was dramatically enhanced when the endbearing the 5′ triphosphate was blunt (Example 3; FIGS. 4-6, samples“3P-X+AS X24”, “3P-X+AS X24+A”, “3P-X+AS X24+2A”, “3P-X+AS X23”). Thesame results were obtained with peripheral blood mononuclear cells(PBMC) depleted of PDCs or PBMCs pre-treated with chloroquine, in whichcases IFN-α production from PDCs was excluded.

This finding is surprising because it contradicts earlier report thatthe presence of blunt end did not enhance the IFN-inducing activity ofdsRNA bearing 5′ triphosphate¹⁵. Furthermore, this finding demonstratesfor the first time that the blunt end has to be on the same side as the5′ triphosphate to be recognized by and activate RIG-I.

This surprising finding suggests that both 5′ triphosphate and blunt endare molecular signatures recognized by RIG-I. Whereas 5′ triphosphate isthe primary molecular signature recognized by RIG-I, blunt end is asecondary one which is not capable of activating RIG-I on its own but iscapable of augmenting RIG-I activation in the presence of 5′triphosphate. Furthermore, the fact that the activity-enhancing effectof the blunt end was only observed when the blunt end was the end thatbore the 5′ triphosphate suggests that 5′ triphosphate and blunt end arerecognized by functional domains or sub-domains of RIG-I which areadjacent to each other in the 3-dimensional structure. In particular, itis highly likely that 5′ triphosphate and blunt end are recognized bythe same domain of RIG-I, the C-terminal regulatory domain.

The present finding is surprising also because the present inventorsfound that dsRNA oligonucleotides as short as 21 base pairs (bp) werecapable of activating RIG-I and inducing significant IFN-α productionwhen they bore 5′ triphosphate and a blunt end, which is in contrast tothe suggestion of Marques et al. (2006) that a length of 25 bp wasrequired for consistent RIG-I activation¹⁶.

Moreover, the present inventors found that the RIG-1-activating andIFN-α-inducing activity of a dsRNA bearing 5′ triphosphate and blunt enddepended on the identity of the 5′ nucleotide bearing the 5′triphosphate. Whereas a dsRNA having a 5′ adenosine (A) was more potentthan one having a 5′ guanosine (G) or one having a 5′ uridine (U), theywere all more potent than one having a 5′ cytidine (C).

Without being bound by any theory, it is hypothesized that chemicallysynthesized dsRNA oligonucleotides are essentially homogenouspopulations, wherein the oligonucleotides in each population arechemically well-defined and have essentially the same length, sequenceand end structures. In contrast, dsRNA oligonucleotides obtained via invitro transcription have variable lengths and end structures.

The present inventors have thus identified synthetic dsRNAoligonucleotides bearing at least one 5′ triphosphate and at least oneblunt end at the same end as the 5′ triphosphate, with a reference for Aas the 5′ triphosphate-bearing nucleoside, as highly potent agents foractivating RIG-I and inducing type I IFN production fromRIG-I-expressing cells.

In addition, it has been reported that certain nucleoside modificationsof the RNA, which occur during eukaryotic post-transcriptionalprocessing of endogenous RNA, abrogated the IFN-α-inducing activity of5′ triphosphate-bearing RNA molecules^(15, 19). One of thesemodifications was 2′-O-methylation.

However, surprisingly, the present inventors found that when the most 3′nucleotide which base pairs with the most 5′ ribonucleotide bearing the5′ triphosphate at the blunt end was 2′-O-methylated, the IFN-α-inducingactivity of the oligonucleotide was not only not abrogated, butenhanced, providing yet another molecule signature which enhances thetype I IFN-inducing activity of an oligonucleotide. At the same time,2′-O-methylation of a nucleotide at any position other than theabove-mentioned position resulted in a decrease in the type IIFN-inducing activity of the oligonucleotide. This finding opens up thepossibility of modulating the type I IFN-inducing activity of anoligonucleotide bearing a 5′ triphosphate by 2′-O-methylation atspecific positions. Whereas the type I IFN-inducing activity of a 5′triphosphate-bearing olignucleotide may be enhanced by 2′-O-methylationof a most 3′ nucleotide which base pairs with a most 5′ ribonucleotidebearing a 5′ triphosphate at a blunt end, the type I IFN-inducingactivity may be reduced by 2′-O-methylation of any other nucleotide,especially the second most 3′ nucleotide which is just 5′ of the most 3′nucleotide which base pairs with a most 5′ ribonucleotide bearing a 5′triphosphate at a blunt end.

Furthermore, the present inventors found that the double strandedoligonucleotides with 5% triphosphate ends having gene-silencingactivity are particularly useful against melanoma, especially anti-bcl-2siRNA with 5′-triphosphate ends (3p-siRNA).

Recognition of 5′-triphosphate by the cytosolic antiviral helicaseretinoic-acid-induced-protein-1 (RIG-I) activated innate immune cellssuch as dendritic cells and directly induced interferon and apoptosis intumor cells. These RIG-1-mediated activities synergized withsiRNA-mediated gene silencing, especially bcl-2 silencing to provokemassive apoptosis of tumor cells in lung metastases in vivo. Thetherapeutic activity required NK cells and interferon, as well assilencing of bcl-2 as evidenced by rescue with a mutated bcl-2 target,by site-specific cleavage of bcl-2 mRNA in lung metastases anddownregulation of bcl-2 protein in tumor cells in vivo. Together,3p-siRNA represents a single molecule-based approach in which RIG-Iactivation on both the immune- and tumor cell level corrects immuneignorance and in which gene silencing governs key molecular events.

Through the mechanism of RNA interference (RNAi) these shortdouble-stranded RNAs can be designed to target mRNAs encoding keyregulators of tumor survival^(45,46). A distinct and independentbiological property of RNA oligonucleotides can be the activation ofimmunoreceptors specialized for the detection of viral nucleic acids.The ubiquitously expressed helicase RIG-I is one of two immunoreceptorsthat signal the presence of viral RNA in the cytosol of cells¹¹.Specifically, RIG-I detects RNA with a triphosphate group at the5′-end^(15,47). Formation of such 5′-triphosphate RNA by RNA polymerasesin the cytosol of cells is characteristic for most negative strand RNAviruses⁴⁸.

Since recognition of 3p-RNA by RIG-I is largely independent of RNAsequence, and gene silencing is not inhibited by the presence of a5′-triphosphate, both biological activities can be combined in one shortdsRNA molecule.

Such a short dsRNA molecule with triphosphate groups at the 5′-end(3p-siRNA) can be designed to target the mRNA of any key tumor survivalfactor. In the case of melanoma, such a molecule is Bcl-2. Bcl-2 wasoriginally found in B cell lymphomas and is involved in the regulationof apoptosis. Overexpression of Bcl-2 is considered to be responsiblefor the extraordinary resistance of melanoma cells to chemotherapy⁴⁹⁻⁵¹.

Therefore the present invention is directed to oligonucleotidepreparations having both immunoreceptor activation ability andgene-silencing activity. Preferably, the oligonucleotide preparations ofthe invention have Bcl-2-silencing and RIG-I activation ability.

DEFINITIONS

The articles “a” and “an” are used herein to refer to one or to morethan one (i.e., at least one) of the grammatical object of the article.By way of example, “an element” means one element or more than oneelement.

All terms used herein bear the meanings that are established in the artunless otherwise noted. Techniques disclosed herein can be performed bya person skilled in the art following the present description and/orestablished protocols, such as those disclosed in Molecular Cloning: ALaboratory Manual (Sambrook et al., 1989, Cold Spring HarbourLaboratory, New York), Current Protocols in Molecular Biology (Ausubelet al., 2007, John Wiley & Sons, New York), and Current Protocols inImmunology (Coligan et al., 2007, John Wiley & Sons, New York).

The expressions “an RNA oligonucleotide bearing 5′ triphosphate”,“triphosphate RNA oligonucleotide” and “3pRNA oligonucleotide” are usedinterchangeably.

The expressions “structural motif” and “molecular signature” are usedinterchangeably.

Oligonucleotides

In the first aspect, the present invention provides an oligonucleotidepreparation which comprises an essentially homogenous population of anoligonucleotide and which is capable of activating RIG-I and inducing ananti-viral response, in particular, a type I IFN response, morespecifically, an IFN-α response.

The oligonucleotide has at least one blunt end and comprises at least 1ribonucleotide at the 5′ end at the blunt end, wherein the blunt endbears a 5′ triphosphate attached to the most 5′ ribonucleotide, whereinthe 5′ triphosphate is free of any cap structure, and wherein the bluntend is followed by a fully double-stranded section which is at least 19,preferably at least 21 base pair (bp) in length. In other words, theblunt end is an/the end of the fully double-stranded section.

By “fully double-stranded”, it is meant that the double-stranded sectionis not interrupted by any single-stranded structures. An oligonucleotidesection is fully double-stranded when the two stretches of nucleic acidforming the section have the same length and have sequences which are100% complementary to each other. As established in the art, twonucleotides are said to be complementary to each other if they can forma base pair, either a Waston-Crick base pair (A-U, G-C) or a wobble basepair (U-G, U-A, I-A, I-U, I-C).

The double-stranded section is preferably at least 20 bp, 21 bp, morepreferably at least 22 bp, 23 bp, even more preferably at least 24 bp,25 bp in length. The double-stranded section is preferably at most 60bp, more preferably at most 50 bp, even more preferably at most 40 bp,most preferably at least 30 bp in length.

The oligonucleotide has preferably at least 2, 3, 4, 5, 6, morepreferably at least 7, 8, 9, 10, 11, 12, even more preferably, at least13, 14, 15, 16, 17, 18, most preferably, at least 19 ribonucleotides atthe 5′ end of the strand bearing the 5′ triphosphate. In the mostpreferred embodiment, the fully double-stranded section is composedsolely of ribonucleotides.

In one embodiment, the oligonucleotide is an RNA oligonucleotide. Inanother embodiment, the oligonucleotide is an RNA-DNA hybrid.

By “an essentially homogenous population”, it is meant that theoligonucleotides contained in the preparation have essentially the samechemical identity (or chemical composition), including the samenucleotide sequence, backbone, modifications, length, and endstructures. In other words, the oligonucleotides contained in thepreparation are chemically defined and are essentially identical to eachother. In particular, it is meant that at least 85%, preferably at least90%, more preferably at least 95%, even more preferably at least 96%,97%, 98%, most preferably at least 99% of the oligonucleotides in thepreparation have the same chemical identity (or chemical composition),including the same nucleotide sequence, backbone, modifications, length,and end structures. In other words, the preparation is at least 85%,preferably at least 90%, more preferably at least 95%, even morepreferably at least 96%, 97%, 98%, most preferably at least 99% pure.The purity and the chemical identity (or chemical composition) of anoligonucleotide preparation can be readily determined by a personskilled in the art using any appropriate methods, such as gelelectrophoresis (in particular, denaturing gel electrophoresis), HPLC,mass spectrometry (e.g., MALDI-ToF MS), and sequencing.

In one embodiment, the oligonucleotide is a double-strandoligonucleotide.

As established in the art and used herein, “a double-strandoligonucleotide” refers to an oligonucleotide which is composed of twosingle strands of oligonucleotide.

Specifically, the double-strand oligonucleotide is one wherein at leastone of the strands comprises at least 1, preferably at least 3, morepreferably at least 6 ribonucleotide(s) at the 5′ end, wherein at leastone of the strands that comprise at least 1 ribonucleotide at the 5′ endhas a triphosphate attached to the most 5′ ribonucleotide, wherein thetriphosphate is free of any cap structure, wherein at least one of theends that bear a 5′ triphosphate is a blunt end, and wherein at leastone of the blunt ends bearing a 5′ triphosphate is followed by a fullydouble-stranded section which is at least 19, preferably at least 21base pair (bp) in length.

In one embodiment, the double-strand oligonucleotide is fullydouble-stranded. In this case, the oligonucleotide is composed of twosingle-stranded oligonucleotides which have the same length and whichhave sequences that are 100% complementary to each other.

In one embodiment, the double-strand oligonucleotide is partiallydouble-stranded. In this case, the two strands forming theoligonucleotide have different lengths, sequences which are not 100%complementary to each other, or both. In other words, the at least onefully double-stranded section of the oligonucleotide is connected with asingle-stranded structure at one or both ends.

In one embodiment, the double-strand oligonucleotide has one blunt endbearing the 5′ triphosphate and one 5′ overhang of 1, 2, 3 or morenucleotide(s) at the other end which may or may not bear a 5′triphosphate. In another embodiment, the double-strand oligonucleotidehas one blunt end bearing the 5′ triphosphate and one 3′ overhang of 1,2, 3 or more nucleotide(s) at the other end which may or may not bear a5′ triphosphate. In yet another embodiment, the double-strandoligonucleotide has one blunt end bearing the 5′ triphosphate and asecond blunt end which may or may not bear a 5′ triphosphate. In afurther embodiment, the double-strand oligonucleotide has two blunt endseach bearing a 5′ triphosphate. In certain embodiments, the 5′ or 3′overhang has 3 or fewer, preferably 2 or fewer, nucleotides.

In one embodiment, the double-strand oligonucleotide has one 5′triphosphate. In another embodiment, the double-strand oligonucleotidehas two 5′ triphosphates. In a preferred embodiment, the second 5′triphosphate is also attached to a 5′ ribonucleotide.

In a preferred embodiment, the double-strand oligonucleotide is fullydouble-stranded or partially double-stranded, comprising only one fullydouble-stranded section which is at least 19, preferably at least 21 bpin length. In a more preferred embodiment, the oligonucleotide ispartially double-stranded and contains one 5′ triphosphate attached tothe most 5′ ribonucleotide at the blunt end and a 3′ overhang of 1 nt atthe other end which is not blunt and does not bear a 5′ triphosphate.

In the case of a fully double-stranded oligonucleotide or a partiallydouble-stranded oligonucleotide comprising only one fullydouble-stranded section, the oligonucleotide is at least 19, preferablyat least 21 bp in length, wherein the length refers to the number ofbase pairs of the continuous section of the oligonucleotide that isfully double-stranded. In other words, the length of the overhang isexcluded from “the length of the double-strand oligonucleotide”. By“continuous”, it is meant that the section of the oligonucleotide thatis fully double-stranded and is not interrupted by any single-strandedstructures. Preferably, the double-strand oligonucleotide is at least20, 21 bp, more preferably at least 22, 23 bp, and most preferably atleast 24, 25 bp in length. Preferably, the double-strand oligonucleotideis at most 60 bp, more preferably at most 50 bp, even more preferably atmost 40 bp, and most preferably at most 30 bp in length.

In one embodiment, the double-strand oligonucleotide is a homoduplex. By“homoduplex”, it is meant that the two strands forming theoligonucleotide have exactly the same length and sequence in the 5′ to3′ orientation. A homoduplex can be formed when each strand forming thedouble-strand oligonucleotide has a sequence that is 100%self-complementary, meaning that the sequence of the 5′ half is 100%complementary to that of the 3′ half.

Various methods for producing oligonucleotides are known in the art.However, in order to obtain an essentially homogeneous population of adouble-strand oligonucleotide, chemical synthesis is the preferredmethod of preparation. The particular method or process of chemicalsynthesis is not important; it is only important that the synthesizedoligonucleotide is purified and quality-controlled such that theoligonucleotide preparation contains essentially a homogenous populationof oligonucleotides having essentially the same chemical identity (orchemical composition), including the same nucleotide sequence, backbone,modifications, length, and end structures. The oligonucleotides can bepurified by any standard methods in the art, such as capillary gelelectrophoresis and HPLC. Synthetic oligonucleotides, eithersingle-strand or double-strand, obtained from most commercial sourcescontain 5′ OH. These synthetic oligonucleotides can be modified at the5′ end to bear a 5′ triphosphate by any appropriate methods known in theart. The preferred method for 5′ triphosphate attachment is thatdeveloped by János Ludwig and Fritz Eckstein²⁷.

Alternatively, in vitro transcription can be employed. However, in orderto obtain the single strands to prepare the a double-strandoligonucleotide by in vitro transcription, measures need to be taken toensure that each in vitro transcribed single strand is indeedsingle-stranded and has the desired sequence. Aberrant transcripts maybe generated in vitro using an RNA polymerase. For example, it ishypothesized that an RNA transcript generated by an RNA polymerase invitro may fold back onto itself and prime RNA-dependent RNA synthesis,leading to the generation of aberrant transcripts of undefined and/ornon-uniform lengths and sequences. Therefore, in principle, any measurethat would prevent RNA synthesis primed by the RNA transcript itself canbe employed.

For example, a single stranded oligonucleotide is designed to have asequence X₁-X₂-X₃- . . . X_(m-2)-X_(m-1)-X_(m), wherein m is the lengthof the oligonucleotide, wherein the sequence has no or minimal selfcomplementarity, wherein X₁, X₂, X₃, . . . , X_(m) are chosen from 1, 2or 3 of the 4 conventional nucleotides A, U, C and G, wherein at leastone of the nucleotides that are complementary to any of X_(m-2),X_(m-1), and X_(m), i.e., Y_(m-2), Y_(m-1), and Y_(m), is not among the1, 2, or 3 nucleotides chosen for X₁, X₂, X₃, . . . , X_(m).

An appropriate DNA template for generating such an ssRNA oligonucleotidecan be generated using any appropriate methods known in the art. An invitro transcription reaction is set up using the DNA template and anucleotide mixture which does not contain the complementarynucleotide(s) which is(are) not comprised in X₁-X₂-X₃- . . .X_(m-2)-X_(m-1)-X_(m). Any appropriate in vitro transcription conditionsknown in the art can be used. Due to the absence of the complementarynucleotide, no aberrant RNA-primed RNA synthesis can take place. As aresult, a single-stranded population of X₁-X₂-X₃- . . . -X_(m) can beobtained. The resulting ssRNA preparation can be purified by anyappropriate methods known in the art and an equal amount of two purifiedssRNA preparations with complementary sequence can be annealed to obtainan essentially homogenous population of a double-strand RNAoligonucleotide of desired sequence.

For example, the ssRNA oligonucleotide may be GACACACACACACACACACACACA(SEQ ID NO: 44) and the in vitro transcription may be carried out in thepresence of ATP, CTP and GTP, i.e., in the absence of UTP.

It is also possible to synthesize the two strands forming thedouble-strand oligonucleotide using different methods. For example, onestrand can be prepared by chemical synthesis and the other by in vitrotranscription. Furthermore, if desired, an in vitro transcribed ssRNAcan be treated with a phosphatase, such as calf intestine phosphotase(CIP), to remove the 5′ triphosphate.

In another embodiment, the oligonucleotide is a single-strandoligonucleotide having a stem-and-loop structure. As established in theart and used herein, “a single-strand oligonucleotide” refers to anoligonucleotide which is composed of one single strand ofoligonucleotide. As established in the art and used herein, astem-and-loop structure contains a stem, which is a fullydouble-stranded section made up of two stretches of nucleic acids whichhave complementary sequences and the same length, and a loop which is asingle-stranded section.

Specifically, the single-strand oligonucleotide has a triphosphate atthe 5′ end and contains at least one stem-and-loop structure, whereinthe stem of at least one of the stem-and-loop structures is composed ofthe 5′ and the 3′ end of the single-strand oligonucleotide, is fullydouble-stranded (i.e., not interrupted by any single-strandedstructures), and is at least 19 bp, preferably at least 21 bp in length,and wherein the end of the stem which is formed by the very 5′ and 3′ends of the oligonucleotide and which is not connect to the loop isblunt. In other words, at least 19, preferably at least 21 nucleotidesat the very 5′ end and at least 21 nucleotides at the very 3′ end of theoligonucleotide have 100% complementarity.

The stem bearing the 5′ triphosphate and the blunt end is preferably atleast 20, 21 bp, more preferably at least 22, 23 bp, and most preferablyat least 24, 25 bp in length. The stem is preferably at most 60 bp, morepreferably at most 50 bp, even more preferably at most 40 bp, and mostpreferably at most 30 bp in length.

The exact size and the sequence of the loop is not critical; it is onlycritical that the loop does not adversely affect the formation and thestability of the stem and does not interfere (e.g., sterically hinder)the interaction between the blunt end and the 5′ triphosphate withRIG-I. The formation of a stem-and-loop structure can be readilypredicted by a person skilled in the art on the basis of the nucleotidesequence of the oligonucleotide and experimentally verified by methodsknown in the art. For example, a ssRNA oligonucleotide can be digestedwith a single-strand-specific RNase and analysed on a denaturing gel.Binding between an oligonucleotide and RIG-I can be readily determinedusing any appropriate methods known in the art, such asimmunoprecipitation¹⁵, fluorescence anisotropy measurement²⁶, and gelshift assay²⁴.

In one embodiment, the single-strand oligonucleotide contains only onestem-and-loop structure.

The single-strand oligonucleotide preparation can be obtained bychemically synthesis or in vitro transcription. The particular method orprocess of preparation is not important; it is only important that theoligonucleotide can be purified and quality-controlled such that theoligonucleotide preparation contains essentially a homogenous populationof oligonucleotides having essentially the same chemical identity (orchemical composition), including the same nucleotide sequence, backbone,modifications, length, and end structures. If the oligonucleotide ischemically synthesized and bears a 5′ OH, a 5′ triphosphate can be addedby any appropriate methods known in the art, preferably the methoddeveloped by János Ludwig and Fritz Eckstein²⁷.

Without being bound by any theory, it is hypothesized that when the 5′and the 3′ nucleotides of a single-strand oligonucleotide have 100%complementarity and the stem has a blunt end, single-strand RNAoligonucleotides having a stem-and-loop (or hairpin) structure and ablunt end with defined sequence, length and end structure can befaithfully obtained by in vitro transcription because of the absence ofaberrant RNA-primed, RNA-dependent transcription. Even though as definedabove, the at least one fully double-stranded section which is at least19, preferably at least 21 bp in length, which has a blunt end and whichbears a 5′ triphosphate at the blunt end is continuously fullydouble-stranded, i.e., not interrupted by any single-stranded structure,this does not have to be the case for an oligonucleotide which iscapable of activating RIG-I and inducing an anti-viral response, inparticular, a type I IFN response, more specifically, an IFN-α response.One or more mismatch(es) may be tolerated in the two stretches ofnucleic acids which form the double-stranded section in that theIFN-inducing activity of the oligonucleotide is not significantlyreduced. In other words, the “fully” double-stranded section may bediscontinuous, i.e., interrupted by one or more single-stranded (orloop) structure(s). An oligonucleotide preparation which comprises anessentially homogenous population of such an oligonucleotide is alsoencompassed by the present invention.

The single-stranded (or loops) structure may occur in one or both of thetwo stretches of nucleic acids which form the double-stranded section.

Preferably, the “fully” double-stranded section is interrupted by atmost 3, more preferably at most 2, even more preferably at most 1single-stranded (or loop) structure(s).

The loops which occur in one or both of the two stretches of nucleicacids which form the double-stranded section may have the same ordifferent length. Preferably, the loop is at most 8, 7 nucleotides (nt),more preferably at most 6, 5 nt, even more preferably at most 4, 3 nt,most preferably at most 2, 1 nt in length. The length of the loop refersto the number of nucleotides in one stretch of nucleic acid which arebetween two adjacent fully stranded-structures and which do not basepair with nucleotides on the other stretch of nucleic acid.

The mismatch is preferably at least 3, 4, 5, 6 bp, more preferably atleast 7, 8, 9, 10, 11, 12 bp, even more preferably at least 13, 14, 15,16, 17, 18 bp away from the blunt end bearing the 5′ triphosphate. Thedistance between a mismatch and the blunt end refers to the number ofnucleotides between the blunt end and the first nucleotide which doesnot form a base pair and which is closest to the blunt end.

Reference is made to FIG. 16 to illustrate the above terms. In the caseof the Sendai viral genome, the double-stranded structure formed by the5′ and 3′ ends of the genomic RNA is interrupted by a loop of 3 nt(5′-UUU-3′) in the stretch of nucleic acid at the 5′ end and notinterrupted by any loop structure in the stretch of nucleic acid at the3′ end. In the case of the Rabies viral genome, the double-strandedstructure formed by the 5′ and 3′ ends of the genomic RNA is interruptedby a loop of 5 nt (5′-AUAAA-3′), followed by a loop of 1 nt (A) followedby a loop of 5 nt (5′-AAUGA-3′) in the stretch of nucleic acid at the 5′end, and interrupted by a loop of 1 nt (G) and a loop of 3 nt(3′-CUA-5′) and a loop of 1 nt (C)) in the stretch of nucleic acid atthe 3′ end.

In one embodiment, the double- or single-strand RNA oligonucleotidecontains one or more GU wobble base pair(s) instead of GC or UA basepairing.

In a preferred embodiment, the double- or single-strand oligonucleotidecomprises at least 1, 2, 3, 4, 5, preferably at least 6, 7, 8, 9, 10,more preferably at least 11, 12, 13, 14, 15, even more preferably atleast 16, 17, 18, 19, 20 inosine (I). In another preferred embodiment,at least 1, 2, 3, 4, 5%, preferably at least 10, 15, 20, 25, 30%, morepreferably at least 35, 40, 45, 50, 55, 60%, even more preferably atleast 70, 80, or 90% of the adenosine (A) and/or guanosine (G) in theoligonucleotide is replaced with inosine (I).

The 5′ ribonucleotide bearing the at least one 5′ triphosphate ispreferably A, followed by G, followed by U, followed by C, in the orderof descending preference.

In preferred embodiments, the sequence of the first 4 ribonucleotides atthe 5′ end of the double- or single-strand oligonucleotide bearing the5′ triphosphate is selected from: AAGU (No. 1), AAAG (No. 2), AUGG (No.3), AUUA (No. 4), AACG (No. 5), AUGA (No. 6), AGUU (No. 7), AUUG (No.8), AACA (No. 9), AGAA (No. 10), AGCA (No. 11), AACU (No. 12), AUCG (No.13), AGGA (No. 14), AUCA (No. 15), AUGC (No. 16), AGUA (No. 17), AAGC(No. 18), AACC (No. 19), AGGU (No. 20), AAAC (No. 21), AUGU (No. 22),ACUG (No. 23), ACGA (No. 24), ACAG (No. 25), AAGG (No. 26), ACAU (No.27), ACGC (No. 28), AAAU (No. 29), ACGG (No. 30), AUUC (No. 31), AGUG(No. 32), ACAA (No. 33), AUCC (No. 34), AGUC (No. 35), wherein thesequence is in the 5′->3′ direction. In more preferred embodiments, thesequence of the first 4 ribonucleotides at the 5′ end of theoligonucleotide bearing the 5′ triphosphate is selected from Nos. 1-19,more preferably from Nos. 1-9, even more preferably from Nos. 1-4. Incertain embodiments, the first nucleotide of the above-listed 5′4-nucleotide sequences is a G, U or C, in the order of descendingpreference, instead of A.

In certain embodiments, the double- or single-strand oligonucleotidecontains one or more structural motif(s) or molecular signature(s) whichis(are) recognized by the TLRs, in particular, TLR3, TLR7 and TLR8.

In one embodiment, the double-strand oligonucleotide or a stem of thesingle-strand oligonucleotide is at least 30 bp in length and isrecognized by TLR3².

In another embodiment, the double-strand oligonucleotide or a stem ofthe single-strand oligonucleotide contains defined sequence motifsrecognized by TLR7^(3, 4, 5, 22, 29). In one preferred embodiment, thedouble-strand oligonucleotide or a stem of the single-strandoligonucleotide comprises at least one, preferably at least two, morepreferably at least three, even more preferably at least four, even morepreferably at least five, and most preferably at least six, of the4-nucleotide (4mer) motifs selected from the group consisting of:

-   -   GUUC (No. 101), GUCA (No. 102), GCUC (No. 103), GUUG (No. 104),        GUUU (No. 105), GGUU (No. 106), GUGU (No. 107), GGUC (No. 108),        GUCU (No. 109), GUCC (No. 110), GCUU (No. 111), UUGU (No. 112),        UGUC (No. 113), CUGU (No. 114), CGUC (No. 115), UGUU (No. 116),        GUUA (No. 117), UGUA (No. 118), UUUC (No. 119), UGUG (No. 120),        GGUA (No. 121), GUCG (No. 122), UUUG (No. 123), UGGU (No. 124),        GUGG (No. 125), GUGC (No. 126), GUAC (No. 127), GUAU (No. 128),        UAGU (No. 129), GUAG (No. 130), UUCA (No. 131), UUGG (No. 132),        UCUC (No. 133), CAGU (No. 134), UUCG (No. 135), CUUC (No. 136),        GAGU (No. 137), GGUG (No. 138), UUGC (No. 139), UUUU (No. 140),        CUCA (No. 141), UCGU (No. 142), UUCU (No. 143), UGGC (No. 144),        CGUU (No. 145), CUUG (No. 146), UUAC (No. 147),        wherein the nucleotide sequences of the motifs are 5′→3′.

Preferably, the 4mer motifs are selected from the group consisting ofNos. 101-119, Nos. 101-118, Nos. 101-117, Nos. 101-116, more preferably,Nos. 101-115, Nos. 101-114, Nos. 101-113, Nos. 101-112, more preferably,Nos. 101-111, Nos. 110-110, Nos. 101-109, No. 101-108, Nos. 101-107,even more preferably, Nos. 101-106, Nos. 101-105, Nos. 101-104, Nos.101-103, most preferably, Nos. 101-102 of the 4mer motifs. Theoligonucleotide may comprise one or more copies of the same 4mer motifor one or more copies of one or more different 4mer motifs.

In yet another embodiment, the double-strand oligonucleotide has oneblunt end which bears a 5′ triphosphate and one end with a 5′ or 3′overhang, wherein the 5′ or 3′ overhang contains defined sequence motifsrecognized by TLR8^(4, 18, 22, 28). In a further embodiment, a loop ofthe single-strand oligonucleotide contains defined sequence motifsrecognized by TLR8. In certain embodiments, the 5′ or 3′ overhang of thedouble-strand oligonucleotide or the loop of the single-strandedoligonucleotide is at least 4, preferably at least 6, more preferably atleast 12, most preferably at least 18 nucleotides in length. Inpreferred embodiments, the 5′ or 3′ overhang of the double-strandoligonucleotide or the loop of the single-strand oligonucleotidecomprises at least one, preferably at least two, more preferably atleast three, even more preferably at least four, even more preferably atleast five, and most preferably at least six, of the 4-nucleotide (4mer)motifs selected from the group consisting of:

-   -   UCGU (No: 201), GUUG (No. 202), UGGU (No. 203), UGGC (No. 204),        GGUA (No. 205), UGAU (No. 206), UGCU (No. 207), UUGC (No. 208),        UUGU (No. 209), UAGU (No. 210), GGUU (No. 211), GUUU (No. 212),        UGUG (No. 213), GUGU (No. 214), UGCC (No. 215), GUAU (No. 216),        GUGC (No. 217), UGUA (No. 218), UGUC (No. 219), CUGU (No. 220),        UGAC (No. 221), UGUU (No. 222), UAAU (No. 223), GUAG (No. 224),        UCUU (No. 225), UUGG (No. 226), UUUG (No. 227), GGAU (No. 228),        UUUU (No. 229), CGUU (No. 230), UUAU (No. 231), GUUC (No. 232),        GUGG (No. 233), GGUG (No. 234), UAUU (No. 235), UCUG (No. 236),        GUAC (No. 237), UAGG (No. 238), UCUC (No. 239), UAGC (No. 240),        UAUC (No. 241), CUAU (No. 242), UACU (No. 243), CGGU (No. 244),        UGCG (No. 245), UUUC (No. 246), UAUG (No. 247), UAAG (No. 248),        UACC (No. 249), UUAG (No. 250), GCUU (No. 251), CAGU (No. 252),        UGAG (No. 253), GAUU (No. 254), GAGU (No. 255), GUUA (No. 256),        UGCA (No. 257), UUCU (No. 258), GCCU (No. 259), GGUC (No. 260),        GGCU (No. 261), UUAC (No. 262), UCAU (No. 263), GCGU (No. 264),        GCAU (No. 265), GAUG (No. 266), GUCU (No. 267), CGUA (No. 268),        CGAU (No. 269),    -   wherein the nucleotide sequences of the motifs are 5′→3′,

Preferably, the 4mer motifs are selected from the group consisting ofNos. 201-211, more preferably Nos. 201-210, Nos. 201-209, Nos. 201-208,even more preferably Nos. 201-207, Nos. 201-206, Nos. 201-205, Nos.201-204, even more preferably Nos. 201-203, Nos. 201-202 of theabove-listed 4mer motifs. Most preferably, the 4mer motif is UCGU (No.201). The oligonucleotide may comprise one or more copies of the same4mer motif or one or more copies of one or more different 4mer motifs.

In a further embodiment, the double-strand oligonucleotide has one bluntend which bears a 5′ triphosphate and one end with a 5′ or 3′ overhang,wherein the 5′ or 3′ overhang is composed of deoxyribonucleotides andcontains defined sequence motifs recognized by TLR9⁶. In anotherembodiment, a loop of the single-strand oligonucleotide is composed ofdeoxyribonucleotides and contains defined sequence motifs recognized byTLR9. In preferred embodiments, the 5′ or 3′ overhang of thedouble-strand oligonucleotide or the loop of the single-strandoligonucleotide comprises one or more unmethylated CpG dinucleotides.

The double- or single-strand oligonucleotide may contains one or more ofthe same or different structural motif(s) or molecular signature(s)recognized by TLR3, TLR7, TLR8 and TLR9 described above.

The double- or single-strand oligonucleotide may contain anynaturally-occurring, synthetic, modified nucleotides, or a mixturethereof, as long as the synthetic and/or modified nucleotides do notcompromise (i.e., reduce) the type I IFN-inducing activity of theoligonucleotide.

In one embodiment, the oligonucleotide does not contain any modificationsuch as pseudouridine, 2-thiouridine, 2′-Fluorine-dNTP, in particular2′-fluorine-dCTP, 2′-fluorine-dUTP.

In another embodiment, the nucleotides of the oligonucleotide, exceptthe most 3′ nucleotide(s) which base pairs with the most 5′ribonucleotide(s) bearing the 5′ triphosphate(s), is(are) free of2′-O-methylation.

In a preferred embodiment, at least one most 3′ nucleotide which basepairs with a most 5′ ribonucleotide bearing a 5′ triphosphate at theblunt end is 2′-O-methylated. More preferably, said most 3′ nucleotideis 2′-O-methylated UTP.

In one embodiment, the oligonucleotide is a single-strandoligonucleotide and contains one 3′ end and thus one most 3′ nucleotide.In one embodiment, the oligonucleotide is a double-strandoligonucleotide and contains two 3′ ends. In one embodiment, thedouble-strand oligonucleotide contains one 5′ triphosphate at one bluntend, and the most 3′ nucleotide which base pairs with the most 5′ribonucleotide bearing a 5′ triphosphate at the blunt end is2′-O-methylated. In one embodiment, the double-strand oligonucleotidecontains two 5′ triphosphates at two blunt ends, and one, preferablyboth of the most 3′ nucleotides at the two blunt ends is/are2′-O-methylated.

The double- or single-strand oligonucleotide may contain anynaturally-occurring, synthetic, modified internucleoside linkages, or amixture thereof, as long as the linkages do not compromise the type IIFN-inducing activity of the oligonucleotide. In one embodiment, theoligonucleotide comprises at least one phosphorothioate linkage and/orat least one pyrophosphate linkage.

The 5′ triphosphate group of the double- or single-strandoligonucleotide may be modified as long as the modification does notcompromise the type I IFN-inducing activity of the oligonucleotide. Forexample, one or more of the oxygen (O) in the triphosphate group may bereplaced with a sulfur (S); the triphosphate group may be modified withthe addition of one or more phosphate group(s).

The double- or single-strand oligonucleotide may be modified covalentlyor non-covalently to improve its chemical stability, resistance tonuclease degradation, ability to across cellular and/or subcellularmembranes, target (organ, tissue, cell type, subcellularcompartment)-specificity, pharmacokinetic properties, biodistribution,or any combinations thereof. For example, phosphorothioate linkage(s)and/or pyrophosphate linkage(s) may be introduced to enhance thechemical stability and/or the nuclease resistance of an RNAoligonucleotide. In another example, the oligonucleotide may becovalently linked to one or more lipophilic group(s) or molecule(s),such as a lipid or a lipid-based molecule, preferably, a cholesterol ora derivative thereof. The lipophilic group or molecule is preferably notattached to the blunt end bearing the 5′ triphosphate. Preferably, themodification does not comprise the type I IFN-inducing activity of theoligonucleotide. Alternatively, a reduction in the type I IFN-inducingactivity of the oligonucleotide caused by the modification is off-set byan increase in the stability and/or delivery and/or other properties asdescribed above.

The double- or single-strand oligonucleotide may bear any combination ofany number of features described above. A preferred double-strandoligonucleotide is an RNA oligonucleotide having one blunt end with one5′ triphosphate attached to a 5′ A and a length of between 21 and 30 bp.A more preferred double-strand oligonucleotide is an RNA oligonucleotidehaving one blunt end bearing one 5′ triphosphate attached to a 5′ A, a5′ overhang of 1 or 2 nt at the other end which does not bear a 5′triphosphate, and a length of between 21 and 30 bp. A preferredsingle-strand oligonucleotide has one stem-and-loop structure with astem that is between 21 and 30 bp in length. Even more preferably, atleast one most 3′ ribonucleotide which base pairs with the most 5′ribonucleotide(s) bearing the 5′ triphosphate(s) at the blunt end(s) is2′-O-methylated in the above-mentioned oligonucleotides.

In the second aspect, the present invention provides an oligonucleotidepreparation which comprises an essentially homogenous population of asingle-strand oligonucleotide, wherein the oligonucleotide has anucleotide sequence which is 100% complementary to at least 19,preferably at least 21 nucleotides at the very 5′ end of the genomic RNAof a negative single-strand RNA virus.

Preferably, the oligonucleotide has a nucleotide sequence which is 100%complementary to at least 20, 21, preferably 22, 23, more preferably 24,25 nucleotides at the very 5′ end of the genomic RNA of the negativesingle-strand RNA virus.

Negative single-strand RNA viruses include, but are not limited to,influenza A virus, Rabies virus, Newcastle disease virus (NDV),vesicular stomatitis virus (VSV), Measles virus, mumps virus,respiratory syncytial virus (RSV), Sendai virus, Ebola virus, andHantavirus.

Without being bound by any theory, such a single-strand oligonucleotideforms a fully double-stranded structure with a blunt end with the 5′ endof the viral genomic RNA which bears a 5′ triphosphate, therebyproviding a more potent RIG-I ligand than the partially double-strandedstructure comprising stem-and-loop structures formed by the 5′ and 3′end of the viral genomic RNA.

The oligonucleotide preparation of the invention can be used, eitheralone or in combination with one or more immunostimulatory agent(s) toinduce an anti-viral response, in particular, an type I IFN, morespecifically, an IFN-α response, against a negative single strand RNAvirus in a virus-specific manner. The oligonucleotide preparation of theinvention can be used, either alone or in combination with one or moreimmunostimulatory agent(s) and/or anti-viral agent(s) to prevent and/ortreat a viral infection, in particular, an infection by a negativesingle-strand RNA virus.

In the third aspect, the present invention provides an oligonucleotidepreparation which comprises an essentially homogenous population of asingle-strand oligonucleotide, wherein the oligonucleotide has anucleotide sequence which is 100% complementary to the nucleotidesequence at the 5′ end of the genomic RNA of a negative single-strandRNA virus between nucleotides 2+m and 2+m+n, wherein m and n areindependently positive integers, wherein m equals to or is greater than1 and is less than or equals to 5, and wherein n equals to or is greaterthan 12, preferably 13, 14, 15, more preferably 16, 17, 18, even morepreferably 19, 20, 21.

Preferably, n equals to or is greater than 20, 21, more preferably 22,23, even more preferably 24, 25. Preferably, n is less than or equals to60, 50, more preferably 40, even more preferably, 30.

Without being bound by any theory, such a single-strand oligonucleotideforms a fully double-stranded structure with a 5′ overhang of 2-6 ntwith the 5′ end of the viral genomic RNA which bears a 5′ triphosphate,thereby providing an inactive RIG-I ligand. Since the oligonucleotidehas a higher degree of complementarity to the 5′ end of the genomicviral RNA than the 3′ end of the genomic viral RNA, it displaces the 3′end of the genomic viral RNA in the double-stranded structure formedbetween the 5′ and the 3′ ends of the genomic viral RNA, therebyconverting an active RIG-I ligand into an inactive RIG-I ligand.

The oligonucleotide preparation of the present invention can be used,either alone or in combination with one or more immunosuppressant, toreduce or even abolish an anti-viral response, in particular, a type IIFN, more specifically, an IFN-α response, against a negativesingle-strand RNA virus in a virus-specific manner to prevent and/orinhibit (i.e., reduce and/or eliminate) detrimental effects caused bythe over-production of type I IFN and/or other components of theanti-viral response.

siRNA Oligonucleotides

In another embodiment, the invention features a short interfering5′-3p-oligonucleotide (3p-siRNA) that downregulates the expression of atarget gene or that directs cleavage of a target RNA, comprising a senseregion and an antisense region, wherein the antisense region comprises anucleotide sequence that is complementary to a nucleotide sequence ofRNA encoded by the target gene or a portion thereof and the sense regioncomprises a nucleotide sequence that is complementary to the antisenseregion.

By “complementarity” is meant that a nucleic acid can form hydrogenbond(s) with another nucleic acid sequence by either traditionalWatson-Crick including G-U-wobble base pairing or other non-traditionaltypes as described herein. In one embodiment, a double stranded nucleicacid molecule of the invention, such as an siRNA molecule, where onestrand comprises nucleotide sequence that is referred to as the senseregion and the other strand comprises a nucleotide sequence that isreferred to as the antisense region, wherein each strand is between 15and 30 nucleotides in length, comprises between about 10% and about 100%(e.g., about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%)complementarity between the sense region and the antisense region of thedouble stranded nucleic acid molecule. In reference to the nucleicoligonucleotides of the present invention, the binding free energy for anucleic acid molecule with its complementary sequence is sufficient toallow the relevant function of the nucleic acid to proceed, e.g., RNAiactivity. Determination of binding free energies for nucleic acidmolecules is well known in the art (see, e.g., Turner et al., 1987, CSHSymp. Quant. Biol. Lll pp. 123-133; Frier et al., 1986, Proc. Nat. Acad.Sci. USA 83:9373-9377; Turner et al., 1987, J. Am. Chem. Soc.109:3783-3785). A percent complementarity indicates the percentage ofcontiguous residues in a nucleic acid molecule that can form hydrogenbonds (e.g., Watson-Crick base pairing) with a second nucleic acidsequence (e.g., 5, 6, 7, 8, 9, or 10 nucleotides out of a total of 10nucleotides in the first oligonucleotide being based paired to a secondnucleic acid sequence having 10 nucleotides represents 50%, 60%, 70%,80%, 90%, and 100% complementary respectively). In one embodiment, asiRNA molecule of the invention has perfect complementarity between thesense strand or sense region and the antisense strand or antisenseregion of the siRNA oligonucleotide. In one embodiment, a siRNAoligonucleotide of the invention is perfectly complementary to acorresponding target nucleic acid molecule. “Perfectly complementary”means that all the contiguous residues of a nucleic acid sequence willhydrogen bond with the same number of contiguous residues in a secondnucleic acid sequence. In one embodiment, a siRNA oligonucleotide of theinvention comprises about 15 to about 30 or more (e.g., about 15, 16,17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 or more)nucleotides that are complementary to one or more target nucleic acidmolecules or a portion thereof. In one embodiment, a siRNA molecule ofthe invention has partial complementarity (i.e., less than 100%complementarity) between the sense strand or sense region and theantisense strand or antisense region of the siRNA oligonucleotide orbetween the antisense strand or antisense region of the siRNAoligonucleotide and a corresponding target nucleic acid molecule. Forexample, partial complementarity can include various mismatches ornon-based paired nucleotides (e.g., 1, 2, 3, 4, 5 or more mismatches ornon-based paired nucleotides) within the siRNA structure which canresult in bulges, loops, or overhangs that result between the betweenthe sense strand or sense region and the antisense strand or antisenseregion of the siRNA molecule or between the antisense strand orantisense region of the siRNA oligonucleotide and a corresponding targetnucleic acid molecule.

In certain embodiments, the double- or single-strand oligonucleotidedescribed above has gene-silencing activity. As used herein, the term“gene-silencing activity” refers to the capability of theoligonucleotide to downregulate the expression of a gene, preferably viaRNA interference (RNAi). In a preferred embodiment, the oligonucleotideis an siRNA (small interfering RNA) or an shRNA (small hairpin RNA).

In certain embodiments, the double- or single-strand oligonucleotidedescribed above has apoptose-inducing activity. As used herein, the term“apoptose inducing activity” refers to the capability of theoligonucleotide to induce programmed cell-death, preferably viaactivation of RIG-I in tumor cells, preferably via RNA interference(RNAi) in tumor cells, preferably via type-I IFN pathway in tumor cellsor in other cells such as immune cells indirectly contributing toapoptosis induction via the type I IFN receptor expressed in tumorcells. In a preferred embodiment, the oligonucleotide is an siRNA (shortinterfering RNA) or an shRNA (short hairpin RNA).

In one embodiment, the invention features an (3p-siRNA) oligonucleotidethat inhibits, down-regulates, or reduces the expression of a targetgene or that directs cleavage of a target RNA, for example, wherein thetarget gene or RNA comprises protein encoding sequence. In oneembodiment, the invention features a 3p-siRNA oligonucleotide thatdown-regulates expression of a target gene or that directs cleavage of atarget RNA, for example, wherein the target gene or RNA comprisesnon-coding sequence or regulatory elements involved in target geneexpression (e.g., non-coding RNA, miRNA, stRNA etc.). In any of theembodiments herein, the 3p-siRNA oligonucleotide of the inventionmodulates expression of one or more targets via RNA interference or theinhibition of RNA interference. The RNA interference can beRISC-mediated cleavage of the target (e.g., siRNA-mediated RNAinterference). The RNA interference can be translational inhibition ofthe target (e.g., miRNA-mediated RNA interference). In a preferredembodiment, the RNA interference is transcriptional inhibition of thetarget (e.g., siRNA-mediated transcriptional silencing). The RNAinterference generally takes place in the cytoplasm. In one embodiment,the RNA interference can also take place in the nucleus.

In a particularly preferred embodiment the siRNA oligonucleotide has a“combined activity”. As used herein the term “combined activity” refersto the capability of an oligonucleotide to activate RIG-I and to havegene-silencing activity. In other words “combined activity” refers to anoligonucleotide which is both a) capable of activating RIG-I and/orinducing an anti-viral, in particular, an IFN, response in cellsexpressing RIG-I and b) down-regulating expression of a target gene. Theterm “combined” means that the same oligonucleotide exhibits thecombined activities.

In one embodiment, a siRNA oligonucleotide of the invention comprisesmodified nucleotides while maintaining the ability to mediate RNAi. Themodified nucleotides can be used to improve in vitro or in vivocharacteristics such as stability, activity, toxicity, immune response,and/or bioavailability. For example, a siRNA oligonucleotide of theinvention can comprise modified nucleotides as a percentage of the totalnumber of nucleotides present in the siRNA oligonucleotide. As such, asiRNA oligonucleotide of the invention can generally comprise about 5%to about 100% modified nucleotides (e.g., about 5%, 10%, 15%, 20%, 25%,30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or100% modified nucleotides). For example, in one embodiment, betweenabout 5% to about 100% (e.g., about 5%, 10%, 15%, 20%, 25%, 30%, 35%,40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100%modified nucleotides) of the nucleotide positions in a siRNAoligonucleotide of the invention comprise a nucleic acid sugarmodification, such as a 2′-sugar modification, e.g., 2′-O-methylnucleotides, 2′-deoxy-2′-fluoro nucleotides, 2′-deoxy-2′-fluoroarabino,2′-O-methoxyethyl nucleotides, 2′-O-trifluoromethyl nucleotides,2′-O-ethyl-trifluoromethoxy nucleotides, 2′-O-difluoromethoxy-ethoxynucleotides, or 2′-deoxy nucleotides. In another embodiment, betweenabout 5% to about 100% (e.g., about 5%, 10%, 15%, 20%, 25%, 30%, 35%,40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100%modified nucleotides) of the nucleotide positions in a siRNAoligonucleotide of the invention comprise a nucleic acid basemodification, such as inosine, purine, pyridin-4-one, pyridin-2-one,phenyl, pseudouracil, 2,4,6-trimethoxy benzene, 3-methyl uracil,dihydrouridine, naphthyl, aminophenyl, 5-alkylcytidines (e.g.,5-methylcytidine), 5-alkyluridines (e.g., ribothymidine), 5-halouridine(e.g., 5-bromouridine) or 6-azapyrimidines or 6-alkylpyrimidines (e.g.6-methyluridine), or propyne modifications. In another embodiment,between about 5% to about 100% (e.g., about 5%, 10%, 15%, 20%, 25%, 30%,35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100%modified nucleotides) of the nucleotide positions in a siRNAoligonucleotide of the invention comprise a nucleic acid backbonemodification. In another embodiment, between about 5% to about 100%(e.g., about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%,65%, 70%, 75%, 80%, 85%, 90%, 95% or 100% modified nucleotides) of thenucleotide positions in a siRNA oligonucleotide of the inventioncomprise a nucleic acid sugar, base, or backbone modification or anycombination thereof (e.g., any combination of nucleic acid sugar, base,backbone or non-nucleotide modifications). In one embodiment, a siRNAoligonucleotide of the invention comprises at least about 20%, 25%, 30%,35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100%modified nucleotides. The actual percentage of modified nucleotidespresent in a given siRNA oligonucleotide will depend on the total numberof nucleotides present in the siRNA oligonucleotide. If the siRNAoligonucleotide is single stranded, the percent modification can bebased upon the total number of nucleotides present in the singlestranded siRNA oligonucleotides. Likewise, if the siRNA oligonucleotideis double stranded, the percent modification can be based upon the totalnumber of nucleotides present in the sense strand, antisense strand, orboth the sense and antisense strands.

In one embodiment, the invention features a method of modulating theexpression of a target gene in a subject or organism comprising: (a)synthesizing a siRNA oligonucleotide of the invention, which can bechemically-modified, wherein one of the siRNA strands comprises asequence complementary to RNA of the target gene; and (b) introducingthe siRNA oligonucleotide into the subject or organism under conditionssuitable to modulate (e.g., inhibit) the expression of the target genein the subject or organism.

In one embodiment, the invention features a method of modulating theexpression of a target gene within a cell, comprising: (a) synthesizinga siRNA oligonucleotide of the invention, which can bechemically-modified, wherein the siRNA comprises a single strandedsequence having complementarity to RNA of the target gene; and (b)introducing the siRNA oligonucleotide into a cell under conditionssuitable to modulate (e.g., inhibit) the expression of the target genein the cell.

“Modulation” means, in the context of the invention the inhibition,down-regulation, or reduction of the expression of a target gene. By“inhibit”, “down-regulate”, or “reduce”, it is meant that the expressionof the gene, or level of RNA molecules or equivalent RNA moleculesencoding one or more proteins or protein subunits, or activity of one ormore proteins or protein subunits, is reduced below that observed in theabsence of the nucleic acid molecules (e.g., siRNA) of the invention. Inone embodiment, inhibition, down-regulation or reduction with an siRNAoligonucleotide is below that level observed in the presence of aninactive or attenuated molecule. In another embodiment, inhibition,down-regulation, or reduction with siRNA oligonucleotides is below thatlevel observed in the presence of, for example, an siRNA oligonucleotidewith scrambled sequence or with mismatches. In another embodiment,inhibition, down-regulation, or reduction of gene expression with anucleic acid molecule of the instant invention is greater in thepresence of the nucleic acid molecule than in its absence. In oneembodiment, inhibition, down regulation, or reduction of gene expressionis associated with post transcriptional silencing, such as RNAi mediatedcleavage of a target nucleic acid molecule (e.g. RNA) or inhibition oftranslation.

By “gene”, or “target gene” or “target DNA”, is meant a nucleic acidthat encodes an RNA, for example, nucleic acid sequences including, butnot limited to, structural genes encoding a polypeptide. By “targetnucleic acid” or “target polynucleotide” is meant any nucleic acidsequence (e.g., any target and/or pathway target sequence) whoseexpression or activity is to be modulated. The target nucleic acid canbe DNA or RNA. In one embodiment, a target nucleic acid of the inventionis target RNA or DNA.

Given the coding sequence of a gene, a person skilled in the art canreadily design siRNAs and shRNAs using publicly available algorithmssuch as that disclosed in Reynolds et al.²³ and design engines such as“BD-RNAi design” (Beckton Dickinson) and “Block-iT RNAi” (Invitrogen).Even though conventional siRNAs usually are 19 bp in length and have two2-nucleotide 3′ overhangs (i.e., each single strand is 21 nucleotides inlength), a person skilled in the art can readily modify the sequence ofthe siRNAs designed by the known algorithms or design engines and obtaindouble-strand oligonucleotides which have the structural characteristicsof those described above. Furthermore, a person skilled in the art canreadily modify the sequence of shRNA designed to obtain single-strandoligonucleotides which have the structural characteristics of thosedescribed above. Moreover, a person skilled in the art can readily testthe gene-silencing efficacy of the oligonucleotides using methods knownin the art such as Northern blot analysis, quantitative orsemi-quantitative RT-PCR, Western blot analysis, surface orintracellular FACS analysis. One exemplary method for designing siRNAoligonucleotides is outlined below.

The following non-limiting steps can be used to carry out the selectionof siNAs targeting a given gene sequence or transcript.

1. The target sequence is parsed in silico into a list of all fragmentsor subsequences of a particular length, for example 23 nucleotidefragments, contained within the target sequence. This step is typicallycarried out using commercial sequence analysis programs such as Oligo,MacVector, or the GCG Wisconsin Package.2. In some instances the siRNAs may correspond to more than one targetsequence; such would be the case for example in targeting differenttranscripts of the same gene, targeting different transcripts of morethan one gene, or for targeting both the human gene and an animalhomolog. In this case, a subsequence list of a particular length isgenerated for each of the targets, and then the lists are compared tofind matching sequences in each list. The subsequences are then rankedaccording to the number of target sequences that contain the givensubsequence in order to find subsequences that are present in most orall of the target sequences. Alternately, the ranking can identifysubsequences that are unique to a target sequence, such as a mutanttarget sequence. Such an approach would enable the use of siRNA totarget specifically the mutant sequence and not effect the expression ofthe normal sequence.3. In some instances the siRNA subsequences are absent in one or moresequences while present in the desired target sequence; such would bethe case if the siRNA targets a gene with a paralogous family memberthat is to remain untargeted. As in paragraph 2 above, a subsequencelist of a particular length is generated for each of the targets, andthen the lists are compared to find sequences that are present in thetarget gene but are absent in the untargeted paralog.4. The ranked siRNA subsequences can be further analyzed and rankedaccording to GC content. A preference can be given to sites containing30-70% GC, with a further preference to sites containing 40-60% GC.5. The ranked siRNA subsequences can be further analyzed and rankedaccording to self-folding and internal hairpins. Weaker internal foldsare preferred; strong hairpin structures are to be avoided.6. The ranked siRNA subsequences can be further analyzed and rankedaccording to whether they have runs of GGG or CCC in the sequence. GGG(or even more Gs) in either strand can make oligonucleotide synthesisproblematic and can potentially interfere with RNAi activity, so it isavoided whenever better sequences are available. CCC is searched in thetarget strand because that will place GGG in the antisense strand.7. The ranked siRNA subsequences can be further analyzed and rankedaccording to whether they have the dinucleotide UU (uridinedinucleotide) on the 3′-end of the sequence, and/or AA on the 5′-end ofthe sequence (to yield 3′ UU on the antisense sequence). These sequencesallow one to design siRNA oligonucleotides with terminal TT thymidinedinucleotides.8. Four or five target sites are chosen from the ranked list ofsubsequences as described above. For example, in subsequences having 23nucleotides, the right 21 nucleotides of each chosen 23-mer subsequenceare then designed and synthesized for the upper (sense) strand of thesiRNA duplex, while the reverse complement of the left 21 nucleotides ofeach chosen 23-mer subsequence are then designed and synthesized for thelower (antisense) strand of the siRNA duplex. If terminal TT residuesare desired for the sequence (as described in paragraph 7), then the two3′ terminal nucleotides of both the sense and antisense strands arereplaced by TT prior to synthesizing the oligos.9. The siRNA oligonucleotides are screened in an in vitro, cell cultureor animal model system to identify the most active siRNA oligonucleotideor the most preferred target site within the target RNA sequence.

In a preferred embodiment, the siRNA is at least 19 bp, preferably atleast 21 bp in length; the sense strand bears a 5′ triphosphate; the endthat bears the 5′ triphosphate is a blunt end and the other end is ablunt end, a 3′ overhang of 1 or 2 nucleotide(s), or a 5′ overhang of 1or 2 nucleotide(s). Preferably, the end that does not bear 5′triphosphate is a blunt end or a 3′ overhang of 1 or 2 nucleotide(s),more preferably a 3′ overhang of 1 or 2 nucleotide(s).

In preferred embodiments, the siRNA or shRNA is specific for adisease/disorder-associated gene. As widely used in the art, the term “adisease/disorder-related gene” refers to a gene that is expressed in acell in a disease/disorder but not expressed in a normal cell or a genethat is expressed at a higher level in a cell in a disease/disorder thanin a normal cell. In a preferred embodiment, the expression of thedisease/disorder-associated gene causes or contributes to theestablishment and/or progression of the disease/disorder.

In one embodiment, the disease/disorder is a tumor or a cancer and thedisease/disorder-associated gene is an oncogene. Examples of oncogenesinclude wild-type and/or mutant Bcl-2, c-Myc, c-Ras, c-Met, Her2, EGFR,PDGFR, VEGFR, Edg4, Edg7, S1P, Raf, ERK WNT, Survivin, HGF, cdk2, cdk4,MITF, cyclin D1, GRO and mcl-1. A particular preferred oncogene isBcl-2.

In another embodiment, the disease/disorder is a viral infection and thedisease/disorder-associated gene is a gene which is or the product ofwhich is required for host cell recognition, host cell entry, viralreplication, viral practical assembly, and/or viral transmission. Thedisease/disorder-associated gene may be a viral gene or a host gene. Anexample of a viral gene is HbsAg of HBV.

Pharmaceutical Composition

The present invention provides a pharmaceutical composition comprisingat least one of the oligonucleotide preparation of the inventiondescribed above and a pharmaceutically acceptable carrier.

By “at least one”, it is meant that one or more oligonucleotidepreparation(s) of the same or different oligonucleotide(s) can be usedtogether.

In a preferred embodiment, the pharmaceutical composition furthercomprises an agent which facilitates the delivery of the oligonucleotideinto a cell, in particular, into the cytosol of the cell.

In one embodiment, the delivery agent is a complexation agent whichforms a complex with the oligonucleotide and facilitates the delivery ofthe oligonucleotide into cells. Complexation agents are also referred toas “transfection agents” in the art. Any complexation agent which iscompatible with the intended use of the pharmaceutical composition canbe employed. Examples of complexation agents include polymers andbiodegradable microspheres. The polymer is preferably a cationicpolymer, more preferably a cationic lipid. Examples of cationic lipidsinclude DOTAP (Roche) and Lipofectamine (Invitrogen). An other exampleof a lipid-based complexation agent is FuGene (Roche). Examples of apolymer include polyethylenimine (PEI) such as in vivo-jetPEI™(PolyPlus) and collagen derivatives. Examples of biodegradablemicrospheres include liposomes, virosomes, SMARTICLES® (Novosom, Halle),stable-nucleic-acid-lipid particles (SNALPs), SICOMATRIX® (CSL Limited),and poly (D,L-lactide-co-glycolide) copolymer (PLGA) microspheres.

In another embodiment, the delivery agent is a virus, preferably areplication-deficient virus. The oligonucleotide to be delivered iscontained in the viral capsule and the virus may be selected based onits target specificity. Examples of useful viruses includepolymyxoviruses which target upper respiratory tract epithelia and othercells, hepatitis B virus which targets liver cells, influenza viruswhich targets epithelial cells and other cells, adenoviruses whichtargets a number of different cell types, papilloma viruses whichtargets epithelial and squamous cells, herpes virus which targetsneurons, retroviruses such as HIV which targets CD4⁺ T cells, dendriticcells and other cells, modified Vaccinia Ankara which targets a varietyof cells, and oncolytic viruses which target tumor cells. Examples ofoncolytic viruses include naturally occurring wild-type Newcastledisease virus, attenuated strains of reovirus, vesicular stomatitisvirus (VSV), and genetically engineered mutants of herpes simplex virustype 1 (HSV-1), adenovirus, poxvirus and measles virus.

In addition to being delivered by a delivery agent, the oligonucleotideand/or the pharmaceutical composition can be delivered into cells viaphysical means such as electroporation, shock wave administration,ultrasound triggered transfection, and gene gun delivery with goldparticles.

The pharmaceutical composition may further comprise another agent suchas an agent that stabilizes the oligonucleotide. Examples of astabilizing agent include a protein that complexes with theoligonucleotide to form an iRNP, chelators such as EDTA, salts, andRNase inhibitors.

In certain embodiments, the pharmaceutical composition, in particular,the pharmaceutical composition comprising an oligonucleotide preparationaccording to the first and the second aspect of the invention, furthercomprises one or more pharmaceutically active therapeutic agent(s).Examples of a pharmaceutically active agent include immunostimulatoryagents, anti-viral agents, antibiotics, anti-fungal agents,anti-parasitic agents, anti-tumor agents, cytokines, chemokines, growthfactors, anti-angiogenic factors, chemotherapeutic agents, antibodiesand gene silencing agents. Preferably, the pharmaceutically active agentis selected from the group consisting of an immunostimulatory agent, ananti-viral agent and an anti-tumor agent. The more than onepharmaceutically active agents may be of the same or different category.

In certain embodiments, the pharmaceutical composition, in particular,the pharmaceutical composition comprising an oligonucleotide preparationaccording to the first and the second aspect of the invention, furthercomprises an antigen, an anti-viral vaccine, an anti-bacterial vaccine,and/or an anti-tumor vaccine, wherein the vaccine can be prophylacticand/or therapeutic.

In certain embodiments, the pharmaceutical composition, in particular,the pharmaceutical composition comprising an oligonucleotide preparationaccording to the first and the second aspect of the present invention,further comprise retinoid acid, IFN-α and/or IFN-β. Without being boundby any theory, retinoid acid, IFN-α and/or IFN-β are capable ofsensitizing cells for IFN-α production, possibly through theupregulation of RIG-I expression.

The pharmaceutical composition may be formulated in any way that iscompatible with its therapeutic application, including intended route ofadministration, delivery format and desired dosage. Optimalpharmaceutical compositions may be formulated by a skilled personaccording to common general knowledge in the art, such as that describedin Remington's Pharmaceutical Sciences (18th Ed., Gennaro A R ed., MackPublishing Company, 1990).

The pharmaceutical composition may be formulated for instant release,controlled release, timed-release, sustained release, extended release,or continuous release.

The pharmaceutical composition may be administered by any route known inthe art, including, but not limited to, topical, enteral and parenteralroutes, provided that it is compatible with the intended application.Topic administration includes, but is not limited to, epicutaneous,inhalational, intranasal, vaginal administration, enema, eye drops, andear drops. Enteral administration includes, but is not limited to, oral,rectal administration and administration through feeding tubes.Parenteral administration includes, but is not limited to, intravenous,intraarterial, intramuscular, intracardiac, subcutaneous, intraosseous,intradermal, intrathecal, intraperitoneal, transdermal, transmucosal,and inhalational administration.

In a preferred embodiment, the pharmaceutical composition is for local(e.g., mucosa, skin) applications, such as in the form of a spray (i.e.,aerosol) preparation.

The pharmaceutical composition may be use for prophylactic and/ortherapeutic purposes. For example, a spray (i.e., aerosol) preparationmay be used to strengthen the anti-viral capability of the nasal and thepulmonary mucosa.

The optimal dosage, frequency, timing and route of administration can bereadily determined by a person skilled in the art on the basis offactors such as the disease or condition to be treated, the severity ofthe disease or condition, the age, gender and physical status of thepatient, and the presence or absence of previous treatment.

In Vitro Applications

The present application provides the in vitro use of the oligonucleotidepreparation of the invention described above. In particular, the presentapplication provides the use of at least one oligonucleotide preparationfor inducing an anti-viral response, in particular, a type I IFNresponse, more specifically, an IFN-α response, in vitro. The presentapplication also provides the use of at least one oligonucleotidepreparation or at least one siRNA oligonucleotides as described abovefor inducing apoptosis of a tumor cell in vitro.

The present invention provides an in vitro method for stimulating ananti-viral response, in particular, a type I IFN response, morespecifically, an IFN-α response in a cell, comprising the steps of:

-   -   (a) mixing at least one oligonucleotide of the invention        described above with a complexation agent; and    -   (b) contacting a cell with the mixture of (a), wherein the cell        expresses RIG-I.

The cells may express RIG-I endogenously and/or exogenously from anexogenous nucleic acid (RNA or DNA). The exogenous DNA may be a plasmidDNA, a viral vector, or a portion thereof. The exogenous DNA may beintegrated into the genome of the cell or may exist extra-chromosomally.The cells include, but are not limited to, primary immune cells, primarynon-immune cells, and cell lines. Immune cells include, but are notlimited to, peripheral blood mononuclear cells (PBMC), plasmacytoiddendritric cells (PDC), myeloid dendritic cells (MDC), macrophages,monocytes, B cells, natural killer cells, granulocytes, CD4+ T cells,CD8+ T cells, and NKT cells. Non-immune cells include, but are notlimited to, fibroblasts, endothelial cells, epithelial cells, and tumorcells. Cell lines may be derived from immune cells or non-immune cells.

The present invention provides an in vitro method for inducing apoptosisof a tumor cell, comprising the steps of:

-   -   (a) mixing at least one oligonucleotide of the invention        described above with a complexation agent; and    -   (b) contacting a tumor cell with the mixture of (a).

The tumor cell may be a primary tumor cell freshly isolated from avertebrate animal having a tumor or a tumor cell line.

Preferably, the oligonucleotide preparation is according to the firstaspect of the invention described above.

In Vivo Applications

The present application provides the in vivo use of the oligonucleotidepreparation or the siRNA oligonucleotide of the invention describedabove.

In particular, the present application provides at least oneoligonucleotide preparation for inducing an anti-viral response, inparticular, a type I IFN response, more specifically, an IFN-α response,in a vertebrate animal, in particular, a mammal. The present applicationfurther provides at least one oligonucleotide preparation for inducingapoptosis of a tumor cell in a vertebrate animal, in particular, amammal. The present application additionally provides at least oneoligonucleotide preparation for preventing and/or treating a diseaseand/or disorder in a vertebrate animal, in particular, a mammal, inmedical and/or veterinary practice. The invention also provides at leastone oligonucleotide preparation for use as a vaccine adjuvant.

Furthermore, the present application provides the use of at least oneoligonucleotide preparation for the preparation of a pharmaceuticalcomposition for inducing an anti-viral response, in particular, a type IIFN response, more specifically, an IFN-α response, in a vertebrateanimal, in particular, a mammal. The present application furtherprovides the use of at least one oligonucleotide preparation or at leastone siRNA oligonucleotide as described above for the preparation of apharmaceutical composition for inducing apoptosis of a tumor cell in avertebrate animal, in particular, a mammal. The present applicationadditionally provides the use of at least one oligonucleotidepreparation for the preparation of a pharmaceutical composition forpreventing and/or treating a disease and/or disorder in a vertebrateanimal, in particular, a mammal, in medical and/or veterinary practice.

Preferably, the oligonucleotide preparation is according to the firstaspect of the invention described above.

The diseases and/or disorders include, but are not limited to,infections, tumors/cancers, and immune disorders.

Infections include, but are not limited to, viral infections, bacterialinfections, anthrax, parasitic infections, fungal infections and prioninfection.

Viral infections include, but are not limited to, infections byhepatitis C, hepatitis B, influenza virus, herpes simplex virus (HSV),human immunodeficiency virus (HIV), respiratory syncytial virus (RSV),vesicular stomatitis virus (VSV), cytomegalovirus (CMV), poliovirus,encephalomyocarditis virus (EMCV), human papillomavirus (HPV) andsmallpox virus. In one embodiment, the infection is an upper respiratorytract infection caused by viruses and/or bacteria, in particular, flu,more specifically, bird flu.

Bacterial infections include, but are not limited to, infections bystreptococci, staphylococci, E. Coli, and pseudomonas. In oneembodiment, the bacterial infection is an intracellular bacterialinfection which is an infection by an intracellular bacterium such asmycobacteria (tuberculosis), chlamydia, mycoplasma, listeria, and anfacultative intracelluar bacterium such as staphylococcus aureus.

Parasitic infections include, but are not limited to, worm infections,in particular, intestinal worm infection.

In a preferred embodiment, the infection is a viral infection or anintracellular bacterial infection. In a more preferred embodiment, theinfection is a viral infection by hepatitis C, hepatitis B, influenzavirus, RSV, HPV, HSV1, HSV2, and CMV.

In a further preferred embodiment, the present application provides theuse of at least one oligonucleotide preparation or the siRNAoligonucleotide as described above for the preparation of apharmaceutical composition for inducing apoptosis. In a furtherpreferred embodiment, the present application provides the use of atleast one oligonucleotide preparation for the preparation of apharmaceutical composition for both (a) inducing an anti-viral response,in particular, a type I IFN response, more specifically, an IFN-αresponse, and b) downregulation of a tumor target gene, in particularBcl-2, in a vertebrate animal, in particular, a mammal. The presentapplication further provides the use of at least one oligonucleotidepreparation for the preparation of a pharmaceutical composition forinducing apoptosis of a tumor cell in a vertebrate animal, inparticular, a mammal.

Tumors include both benign and malignant tumors (i.e., cancer).

Cancers include, but are not limited to biliary tract cancer, braincancer, breast cancer, cervical cancer, choriocarcinoma, colon cancer,endometrial cancer, esophageal cancer, gastric cancer, intraepithelialneoplasm, leukemia, lymphoma, liver cancer, lung cancer, melanoma,myelomas, neuroblastoma, oral cancer, ovarian cancer, pancreatic cancer,prostate cancer, rectal cancer, sarcoma, skin cancer, testicular cancer,thyroid cancer and renal cancer, preferably the cancer is melanoma.

In certain embodiments, the cancer is selected from hairy cell leukemia,chronic myelogenous leukemia, cutaneous T-cell leukemia, chronic myeloidleukemia, non-Hodgkin's lymphoma, multiple myeloma, follicular lymphoma,malignant melanoma, squamous cell carcinoma, renal cell carcinoma,prostate carcinoma, bladder cell carcinoma, breast carcinoma, ovariancarcinoma, non-small cell lung cancer, small cell lung cancer,hepatocellular carcinoma, basaliom, colon carcinoma, cervical dysplasia,and Kaposi's sarcoma (AIDS-related and non-AIDS related).

Immune disorders include, but are not limited to, allergies, autoimmunedisorders, and immunodeficiencies.

Allergies include, but are not limited to, respiratory allergies,contact allergies and food allergies.

Autoimmune diseases include, but are not limited to, multiple sclerosis,diabetes mellitus, arthritis (including rheumatoid arthritis, juvenilerheumatoid arthritis, osteoarthritis, psoriatic arthritis),encephalomyelitis, myasthenia gravis, systemic lupus erythematosis,autoimmune thyroiditis, dermatisis (including atopic dermatitis andeczematous dermatitis), psoriasis, Siogren's Syndrome, Crohn's disease,aphthous ulcer, iritis, conjunctivitis, keratoconjunctivitis, ulcerativecolitis, asthma, allergic asthma, cutaneous lupus erythematosus,scleroderma, vaginitis, proctitis, drug eruptions, leprosy reversalreactions, erythema nodosum leprosum, autoimmune uveitis, allergicencephalomyelitis, acute necrotizing hemorrhagic encephalopathy,idiopathic bilateral progressive sensorineural hearing loss, aplasticanemia, pure red cell anemia, idiopathic thrombocytopenia,polychondritis, Wegener's granulomatosis, chronic active hepatitis,Stevens-Johnson syndrome, idiopathic sprue, lichen planus, Graves'disease, sarcoidosis, primary biliary cirrhosis, uveitis posterior, andinterstitial lung fibrosis.

Immunodeficiencies include, but are not limited to, spontaneousimmunodeficiency, acquired immunodeficiency (including AIDS),drug-induced immunodeficiency or immunosuppression (such as that inducedby immunosuppressants used in transplantation and chemotherapeuticagents used for treating cancer), and immunosuppression caused bychronic hemodialysis, trauma or surgical procedures.

In a preferred embodiment, the immune disorder is multiple sclerosis.

In certain preferred embodiments, the oligonucleotide has gene silencingactivity. The oligonucleotide thus has two functionalities, genesilencing and immune stimulating, combined in one molecule. In preferredembodiments, the oligonucleotide has gene-silencing activity that isspecific for a disease/disorder-associated gene, such as an oncogene ora gene required for viral infection and/or replication.

In certain embodiments, the oligonucleotide is used in combination withone or more pharmaceutically active agents such as immunostimulatoryagents, anti-viral agents, antibiotics, anti-fungal agents,anti-parasitic agents, anti-tumor agents, cytokines, chemokines, growthfactors, anti-angiogenic factors, chemotherapeutic agents, antibodiesand gene silencing agents. Preferably, the pharmaceutically active agentis selected from the group consisting of an immunostimulatory agent, ananti-viral agent and an anti-tumor agent. The more than onepharmaceutically active agents may be of the same or different category.

In one embodiments, the oligonucleotide is used in combination with anantigen, an anti-viral vaccine, an anti-bacterial vaccine, and/or ananti-tumor vaccine, wherein the vaccine can be prophylactic and/ortherapeutic. The oligonucleotide can serve as an adjuvant.

In another embodiment, the oligonucleotide is used in combination withretinoic acid and/or type I IFN (IFN-α and/or IFN-β). Without beingbound by any theory, retinoid acid, IFN-α and/or IFN-β are capable ofsensitizing cells for IFN-α production, possibly through theupregulation of RIG-I expression.

In other embodiments, the pharmaceutical composition is for use incombination with one or more prophylactic and/or therapeutic treatmentsof diseases and/or disorders such as infection, tumor, and immunedisorders. The treatments may be pharmacological and/or physical (e.g.,surgery, radiation).

Vertebrate animals include, but are not limited to, fish, amphibians,birds, and mammals. Mammals include, but are not limited to, rats, mice,cats, dogs, horses, sheep, cattle, cows, pigs, rabbits, non-humanprimates, and humans. In a preferred embodiment, the mammal is human.

The present application provides at least one oligonucleotidepreparation according to the second aspect of the invention describedabove for inducing an anti-viral response, in particular, a type I IFNresponse, more specifically, an IFN-α response, in a vertebrate animal,in particular, a mammal which is infected with a negative single-strandRNA virus. The present application also provides at least oneoligonucleotide preparation according to the second aspect of theinvention described above for preventing and/or treating an infection bya negative single-strand RNA virus in a vertebrate animal, inparticular, a mammal, in medical and/or veterinary practice.

Furthermore, the present application provides the use of at least oneoligonucleotide preparation according to the second aspect of theinvention described above for the preparation of a pharmaceuticalcomposition for inducing an anti-viral response, in particular, a type IIFN response, more specifically, an IFN-α response, in a vertebrateanimal, in particular, a mammal which is infected with a negativesingle-strand RNA virus. The present application also provides the useof at least one oligonucleotide preparation according to the secondaspect of the invention described above for the preparation of apharmaceutical composition for preventing and/or treating an infectionby a negative single-strand RNA virus in a vertebrate animal, inparticular, a mammal, in medical and/or veterinary practice.

In certain embodiments, the oligonucleotide is used in combination withone or more pharmaceutically active agents such as immunostimulatoryagents, anti-viral agents, cytokines, chemokines, growth factors,antibodies and gene silencing agents. Preferably, the pharmaceuticallyactive agent is selected from an immunostimulatory agent or ananti-viral agent. The more than one pharmaceutically active agents maybe of the same or different category.

In one embodiments, the oligonucleotide is used in combination with ananti-viral vaccine, wherein the vaccine can be prophylactic and/ortherapeutic.

In another embodiment, the oligonucleotide is used in combination withretinoic acid and/or type I IFN (IFN-α and/or IFN-β). Without beingbound by any theory, retinoid acid, IFN-α and/or IFN-β are capable ofsensitizing cells for IFN-α production, possibly through theupregulation of RIG-I expression.

In other embodiments, the pharmaceutical composition is for use incombination with one or more prophylactic and/or therapeutic treatmentsof a viral infection.

The present invention provides at least one oligonucleotide preparationaccording to the third aspect of the invention described above forpreventing and/or inhibiting an anti-viral, in particular, an type IIFN, more specifically an IFN-α response against a negativesingle-strand RNA virus in a mammal. The present invention also providesthe use of at least one oligonucleotide preparation according to thethird aspect of the invention described above for the preparation of apharmaceutical composition for preventing and/or inhibiting ananti-viral, in particular, an type I IFN, more specifically an IFN-αresponse against a negative single-strand virus in a mammal.

In one embodiment, the oligonucleotide preparation may be used fortreating virus-induced hemorrhagic fever. Virus-induced hemorrhagicfever includes, but is not limited to, hemorrhagic fever induced byEbola virus, Marburg virus, Lassa fever virus, the New Worldarenaviruses (Guanarito, Machupo, Junin, and Sabia), Rift Valley fevervirus, and Crimean Congo hemorrhagic fever viruses.

The oligonucleotide preparation may be used alone or in combinationswith one or more immunosuppressant.

Negative single-strand RNA viruses include, but are not limited to,influenza A virus, Rabies virus, Newcastle disease virus (NDV),vesicular stomatitis virus (VSV), Measles virus, mumps virus,respiratory syncytial virus (RSV), Sendai virus, Ebola virus, andHantavirus.

Methods for Preparing an Oligonucleotide Preparation

The present invention provides a method for preparing an oligonucleotidepreparation of the first aspect of the invention described above.

Specifically, the present invention provides a method for preparing adouble-strand oligonucleotide preparation having immunostimulatory, inparticular, type I IFN-inducing, more specifically IFN-α-inducingactivity, comprising the steps of:

(a) identifying two oligonucleotide sequences, wherein at least one ofthe nucleotide sequences comprises at least 1 ribonucleotide at the 5′end, wherein the sequence of the at least 19, preferably at least 21nucleotides at the 5′ end of the at least one oligonucleotide sequencewhich comprises at least 1 ribonucleotide at the 5′ end has 100%complementarily with the sequence of the at least 19, preferably atleast 21 nucleotides at the 3′ end of the other oligonucleotidesequence, thereby forming a blunt end;(b) preparing two essentially homogenous populations of twooligonucleotides having the sequences identified in (a), wherein the atleast one oligonucleotide which comprises at least 1 ribonucleotide atthe 5′ end which forms the blunt end bears a 5′ triphosphate on the most5′ ribonucleotide;(c) preparing an essentially homogenous population of a double-strandoligonucleotide from the two oligonucleotides prepared in (b); and(d) optionally testing the type I IFN-inducing activity of thedouble-strand oligonucleotide.

In one embodiment, the oligonucleotide contained in the oligonucleotidepreparation prepared by the above method has one blunt end bearing one5′ triphosphate or two blunt ends each bearing one 5′ triphosphate. Inone embodiment, the oligonucleotide contained in the oligonucleotidepreparation prepared by the above method has one blunt end bearing one5′ triphosphate and one 5′ overhang of 1 or 2 nucleotides which does notbear any 5′ triphosphate.

Furthermore, the present invention provides a method for preparing asingle-strand oligonucleotide preparation having immunostimulatory, inparticular, type I IFN-inducing, more specifically IFN-α-inducingactivity, comprising the steps of:

(a) identifying an oligonucleotide sequence, wherein the nucleotidesequence comprises at least 1 ribonucleotide at the 5′ end, wherein thesequence of the at least 19, preferably at least 21 nucleotides at the5′ end of the oligonucleotide sequence has 100% complementarily with thesequence of the at least 19, preferably at least 21 nucleotides at the3′ end of the oligonucleotide sequence;(b) preparing an essentially homogenous population of an oligonucleotidehaving the sequence identified in (a), wherein the oligonucleotide bearsa 5′ triphosphate on the most 5′ ribonucleotide; and(c) optionally testing the type I IFN-inducing activity of thesingle-strand oligonucleotide.

In a preferred embodiment, the at least one ribonucleotide at the 5′end, which forms the blunt end, of the oligonucleotide sequenceidentified in the above methods is an A.

In further preferred embodiments, the sequence of the first 4ribonucleotides at the 5′ end, which forms the blunt end, of theoligonucleotide sequence identified in the above methods is selectedfrom: AAGU (No. 1), AAAG (No. 2), AUGG (No. 3), AUUA (No. 4), AACG (No.5), AUGA (No. 6), AGUU (No. 7), AUUG (No. 8), AACA (No. 9), AGAA (No.10), AGCA (No. 11), AACU (No. 12), AUCG (No. 13), AGGA (No. 14), AUCA(No. 15), AUGC (No. 16), AGUA (No. 17), AAGC (No. 18), AACC (No. 19),AGGU (No. 20), AAAC (No. 21), AUGU (No. 22), ACUG (No. 23), ACGA (No.24), ACAG (No. 25), AAGG (No. 26), ACAU (No. 27), ACGC (No. 28), AAAU(No. 29), ACGG (No. 30), AUUC (No. 31), AGUG (No. 32), ACAA (No. 33),AUCC (No. 34), AGUC (No. 35), wherein the sequence is in the 5′->3′direction. In more preferred embodiments, the sequence of the first 4ribonucleotides is selected from Nos. 1-19, more preferably from Nos.1-9, even more preferably from Nos. 1-4.

In an embodiment, the methods further comprises the step of2′-O-methylating the most 3′ nucleotide which base pairs with the most5′ ribonucleotide which bears the 5′ triphosphate and which forms theblunt end.

The present invention further relates to a method for preparing anoligonucleotide preparation having the combined activity of targetgene-silencing and type I IFN-inducing activity, comprising the stepsof: (a) identifying an oligonucleotide sequence, wherein the nucleotidesequence is specific for the target gene and comprises at least 1ribonucleotide at the 5′ end, wherein the sequence of the at least 19,preferably at least 21 nucleotides at the 5′ end of the oligonucleotidesequence has 100% complementarily with the sequence of the at least 19,preferably at least 21 nucleotides at the 3′ end of the sameoligonucleotide sequence; (b) preparing an essentially homogenouspopulation of an oligonucleotide having the sequence identified in (a),wherein the oligonucleotide bears a 5′ triphosphate on the most 5′ribonucleotide; bears a 5′triphosphate at both most 5′ribonucleotide, orjust one at the one or the other 5′end of a double strand RNAoligonucleotide (c) optionally testing the type I IFN-inducing activityof the single-strand oligonucleotide; and (d) optionally testing theoligonucleotide for gene-silencing activity.

The present invention further relates to a method for preparing anoligonucleotide preparation having the combined activity of targetgene-silencing and type I IFN-inducing activity, comprising the stepsof: (a) identifying a nucleotide sequence for a first oligonucleotide,wherein the nucleotide sequence is specific for the target gene; (b)preparing an essentially homogenous population of the firstoligonucleotide having the sequence identified in (a), (c) preparing aessentially homogenous population of a second oligonucleotide whereinthe nucleotide sequence of the second oligonucleotide is 100%complementary to the nucleotide sequence of the first oligonucleotide;(d) optionally testing the type I IFN-inducing activity of thesingle-strand oligonucleotide; and (e) optionally testing theoligonucleotide for gene-silencing activity; wherein the first and/orthe second oligonucleotide bears a 5′ triphosphate on the most 5′ribonucleotide or on both 5′ ribonucleotides; wherein the 5′triphosphate is free of any cap structure; and wherein the first and thesecond oligonucleotide has at least 19, preferably at least 21, morepreferably at least 24 base pairs in length.

Methods for Modulating the Immunostimulatory Activity of anOligonucleotide

The present invention provides a method for enhancing theimmunostimulatory, in particular, type I IFN-inducing, more specificallyIFN-α-inducing activity of an oligonucleotide, wherein theoligonucleotide has at least one blunt end and comprises at least 1ribonucleotide at the 5′ end at the blunt end, wherein the blunt endbears a 5′ triphosphate attached to the most 5′ ribonucleotide, whereinthe 5′ triphosphate is free of any cap structure, and wherein the bluntend is followed by a fully double-stranded section which is at least 19,preferably at least 21 base pair (bp) in length, comprising the step of2′-O-methylating the most 3′ nucleotide which base pairs with the most5′ ribonucleotide bearing the 5′ triphosphate at the blunt end.

The present invention also provides a method for reducing theimmunostimulatory, in particular, type I IFN-inducing, more specificallyIFN-α-inducing activity of an oligonucleotide, wherein theoligonucleotide has at least one blunt end and comprises at least 1ribonucleotide at the 5′ end at the blunt end, wherein the blunt endbears a 5′ triphosphate attached to the most 5′ ribonucleotide, whereinthe 5′ triphosphate is free of any cap structure, and wherein the bluntend is followed by a fully double-stranded section which is at least 19,preferably at least 21 base pair (bp) in length, comprising the step of2′-O-methylating a nucleotide which is not the most 3′ nucleotide whichbase pairs with the most 5′ ribonucleotide bearing the 5′ triphosphateat the blunt end.

In a preferred embodiment, the nucleotide to be 2′-O-methylated is thenucleotide immediately 5′ to the most 3′ nucleotide which base pairswith the most 5′ ribonucleotide bearing the 5′ triphosphate at the bluntend.

The present invention is illustrated by the following Examples.

The Examples are for illustration purposes only and are by no means tobe construed to limit the scope of the invention.

EXAMPLES Materials and Methods 1. Cells

Human PBMC were prepared from whole blood donated by young healthydonors by Ficoll-Hypaque density gradient centrifugation (Biochrom,Berlin, Germany). PDC were isolated by MACS using the blood dendriticcell Ag (BCDA)-4 dendritic cell isolation kit from Miltenyi Biotec(Bergisch-Gladbach, Germany). Briefly, PDC were labelled withanti-BDCA-4 Ab coupled to colloidal paramagnetic microbeads and passedthrough a magnetic separation column twice (LS column, then MS column;Miltenyi Biotec). The purity of isolated PDC (lineage-negative,MHC-II-positive and CD123-positive cells) was above 95%. Beforeisolation of monocytes, PDC were depleted by MACS (LD column; MiltenyiBiotec) and then monocytes were isolated using the monocyte isolationkit II (Miltenyi Biotec). MDCs were purified from PBMC by immunomagneticsorting with anti-CD1c beads (CD1c (BDCA-1)+Dendritic Cell IsolationKit, human, Miltenyi Biotec). Viability of all cells was above 95%, asdetermined by trypan blue exclusion. Unless indicated otherwise, cellswere cultured in 96-well plates for stimulation experiments. MDCs(0.5×10⁶/ml) were kept in RPMI 1640 containing 10% FCS, 1.5 mML-glutamine, 100 U/ml penicillin and 100 μg/ml streptomycin. PDCs(0.25×10⁶/ml) were cultured in the same medium supplemented with 10ng/ml IL-3 (R&D Systems GmbH). Monocytes (0.5×10⁶/ml) were resuspendedin RPMI medium with 2% AB serum (BioWhittaker, Heidelberg, Germany), 1.5mM L-glutamine, 100 U/ml penicillin and 100 μg/ml streptomycin. Allcompounds were tested for endotoxin contamination prior to use.

2. Mice

TLR7-deficient (TLR7^(−/−)) mice were kindly provided by S. Akira³.Female C57BL/6 mice were purchased from Harlan-Winkelmann (Borchen,Germany). Mice were 6-12 weeks of age at the onset of experiments.Animal studies were approved by the local regulatory agency (Regierungvon Oberbayern, Munich, Germany).

3. RNAs

Chemically synthesized RNA oligonucleotides were purchased fromEurogentec (Leiden, Belgium), MWG-BIOTECH AG (Ebersberg, Germany),biomers.net GmbH (Ulm, Germany), and optionally modified by Janos Ludwig(Rockefeller Univ., USA). In vitro transcribed RNAs were prepared usingthe Megashort Script Kit (Ambion, Huntingdon, UK) following themanufacture's instructions. In vitro transcription was carried outovernight at 37° C. The DNA template was digested using DNase I(Ambion). RNAs were purified by phenol:chloroform extraction and alcoholprecipitation. Excess salts and NTPs were removed by passing the RNAsthrough a Mini Quick Spin™ Oligo Column (Roche). Size and integrity ofRNAs was checked via gel electrophoresis. CpG-ODN was purchased fromColey Pharmaceutical Group (Wellesley, USA) or Metabion (Martinsried,Germany). The 2′-O-methylated oligonucleotides were obtained frombiomers.net GmbH.

4. Cell Stimulation (Transfection)

Unless otherwise indicated, 200 ng of the purified RNA oligonucleotideswere transfected into cells using 0.5 μl of Lipofectamine 2000(Invitrogen) in each well of a 96-well plate according to themanufacturer's protocol. CpG ODN was used at a final concentration of 3μg/ml. For transfection with the polycationic polypeptidepoly-L-arginine (Sigma, P7762), 200 ng nucleic acid diluted in PBS (PAALaboratories GmBH) were mixed with 280 ng poly-L-arginine and incubatedfor 20 min prior to stimulation. In some experiments, cells werepre-treated with 1 or 2.5 μg/ml chloroquine (Sigma) for 30 min prior tostimulation. 24 h post-stimulation/transcription, tissue culturesupernatants were collected and assayed for IFN-α production.

5. IFN-α ELISA

Human IFN-α was assessed in cell culture supernatants harvested 24 hoursafter stimulation/transfection using the IFN-α module set (BenderMedSystems, Graz, Austria) according to manufacturer's recommendations.Murine IFN-α was measured according to the following protocol:monoclonal rat anti-mouse IFN-α (clone RMMA-1) was used as the captureAb, polyclonal rabbit anti-mouse IFN-α serum was used for detection(both PBL Biomedical Laboratories), and HRP-conjugated donkeyanti-rabbit IgG was used as the secondary reagent (JacksonImmunoResearch Laboratories). Mouse rIFN-α (PBL Biomedical Laboratories)was used as the standard (IFN-α concentration in IU/ml).

Results Example 1 RNA Oligonucleotides Bearing 5′ Triphosphate areRecognized by Different Receptors in Monocytes and PDCs

PDCs, MDCs and monocytes were all found to be able to respond tostimulation of RNA oligonucleotides bearing 5′ triphosphate (3pRNA) byproducing IFN-α (data not shown). To identify the receptors involved inthe recognition of 3pRNA in these different immune cell populations, invitro transcribed 3pRNA (Table 1) were transfected into these cells inthe presence and absence of chloroquine, a potent inhibitor of TLR7,TLR8 and TLR9-mediated nucleic aid recognition.

TABLE 1 RNA and DNA oligonucleotide sequences. name sequence typeSEQ ID NO GA 5′-pppGGGGGGGGGGGAAAAAAAAAAAA-3′ RNA, in vitro transcribed1 GFPs 5′-pppGGGGCUGACCCUGAAGUUCAUCUU-3′ RNA, in vitro transcribed 2SynRNA 5′-oHGGGGCUGACCCUGAAGUUCAUCUU-3′ RNA, synthetic 2 3pRNA5′-pppGGGGCUGACCCUGAAGUUCAUCUU-3′ RNA, in vitro transcribed 2 CpG5′-GGGGGACGATCGTC GGGGGG-3′ DNA, synthetic 3 (ppp: triphosphate; underlined letters: phosphorothioate linkage 3′ of the base; bold letters,CpG dinucleotides)

As shown in FIG. 1A, whereas 3pRNA-induced IFN-α production frommonocytes was not affected by the addition of chloroquine, 3pRNA-inducedIFN-α production from PDCs was greatly diminished by the addition ofchloroquine.

Furthermore, as shown in FIG. 1A, the ability of 3pRNA to induce IFN-αfrom PDCs depended on the presence of U in the sequence which is knownto be a molecular signature recognized by TLR7.

Moreover, as shown in FIG. 1B, whereas PDCs from wild-type miceresponded to stimulation by 3pRNA by producing IFN-α, this response wasdramatically diminished, if not completely absent, in PDCs fromTLR7-deficient (TLR7^(−/−)) mice.

Taken together, these results suggest that whereas the recognition of3pRNA in PDCs is primarily mediated by TLR7 in a nucleotidesequence-dependent manner, the recognition of 3pRNA in monocytes isprimarily, if not entirely, mediated by RIG-I and is nucleotidesequence-independent.

Example 2 IFN-α Induction in Monocytes Strictly Requires the Presence ofa 5′ Triphosphate

Synthetic RNA oligonucleotides bearing 5′ monophosphate (Table 2) weretransfected into purified primary human monocytes. An in vitrotranscribed RNA bearing 5′ triphosphate was used as a positive control.The level of IFN-α secretion was determined 24 hours aftertransfection/stimulation.

TABLE 2 RNA oligonucleotide sequences. name sequence type SEQ ID NO 27 +0 s 5′-OHAAGCUGACCCUGAAGUUCAUCUGCACC-3′ RNA, synthetic 4 27 + 0 a5′-OHGGUGCAGAUGAACUUCAGGGUCAGCUU-3′ RNA, synthetic 5 27 + 0 ds5′-OHAAGCUGACCCUGAAGUUCAUCUGCACC-3′ RNA, synthetic3′-UUCGACUGGGACUUCAAGUAGACGUGGOH-5′ 27 + 2 s5′-OHGCUGACCCUGAAGUUCAUCUGCACCACUU-3′ RNA, synthetic 6 27 + 2 a5′-OHGUGGUGCAGAUGAACUUCAGGGUCAGCUU-3′ RNA, synthetic 7 27 + 2 ds5′-OHGCUGACCCUGAAGUUCAUCUGCACCACUU-3′ RNA, synthetic3′-UUCGACUGGGACUUCAAGUAGACGUGGUGOH-5′ 3pRNA5′-pppGGGGCUGACCCUGAAGUUCAUCUU-3′ RNA, in vitro 2 transcribed CpG-A5′-GGGGGACGATCGTC GGGGGG-3′ DNA 3 (p: monophosphate; ppp: triphosphate;under lined letters: phosphorothioate linkage 3′ of the base; boldletters, CpG dinucleotides)

As shown in FIG. 2B, regardless of the presence or the absence of a 5′triphosphate, all RNA oligonucleotides tested were capable of inducingIFN-α production from PDCs which primarily use TLR7 for short dsRNArecognition (see Example 1).

As shown in FIG. 2B, whereas in vitro transcribed RNA oligonucleotide,3pRNA, bearing 5′ triphosphate, induced a significant amount of IFN-α,synthetic RNA oligonucleotides bearing 5′ OH failed to induce any IFN-αproduction from monocytes, regardless whether the oligonucleotide hadblunt ends or 3′ overhangs.

These results indicate that 5′ triphosphate is strictly required forIFN-α induction in monocytes. Since RNA recognition and IFN-α inductionis primarily mediated by RIG-I in monocytes (see Example 1), this datasuggest that blunt end is not recognized by RIG-I, at least not in theabsence of 5′ triphosphate.

Example 3 Blunt End Augments the Immunostimulatory Activity of SyntheticDouble-Stranded Oligonucleotides Bearing 5′ Triphosphate

Since 3pRNA oligonucleotides are capable of inducing IFN-α productionfrom PDCs via a TLR7-dependent pathway (see Example 1), in order tostudy RIG-1-dependent induction of IFN-α, RNA oligonucleotides (FIG. 3 &Table 3) were transfected into purified monocytes, PDC-depleted PBMCs(PBMC-PDC) or chloroquine-treated PBMCs (PBMC+Chl).

The design and the designation of the RNA oligonucleotides are shown inFIG. 3 and the sequences of the oligonucleotides are shown in Table 3.

TABLE 3 RNA and DNA oligonucelotide sequences Name Sequence 5′ end TypeSEQ ID NO 3P-A A ACACACACACACACACACACUUU 3P RNA, syn 8 ivt3P-G GACACACACACACACACACACUUU 3P RNA, ivt 9 3P-G G ACACACACACACACACACACUUU 3PRNA, syn 9 3P-C C ACACACACACACACACACACUUU 3P RNA,syn 10 3P-U UACACACACACACACACACACUUU 3P RNA,syn 11 HO-A A ACACACACACACACACACACUUU OHRNA,syn 8 P-A A ACACACACACACACACACACUUU P RNA, syn 8 AS A26AAAGUGUGUGUGUGUGUGUGUGUUGU OH RNA, syn 12 AS A25AAAGUGUGUGUGUGUGUGUGUGUUG OH RNA, syn 13 AS A24 + 2AAAAAAGUGUGUGUGUGUGUGUGUGUU OH RNA, syn 14 AS A24 + AAAAAGUGUGUGUGUGUGUGUGUGUU OH RNA, syn 15 AS A24 AAAGUGUGUGUGUGUGUGUGUGUUOH RNA, syn 16 AS A23 AAGUGUGUGUGUGUGUGUGUGUU OH RNA, syn 17 AS A21GUGUGUGUGUGUGUGUGUGUU OH RNA, syn 18 AS A20 UGUGUGUGUGUGUGUGUGUU OHRNA, syn 19 AS A19 GUGUGUGUGUGUGUGUGUU OH RNA, syn 20 AS A17GUGUGUGUGUGUGUGUU OH RNA, syn 21 AS A15 GUGUGUGUGUGUGUU OH RNA, syn 22AS A13 GUGUGUGUGUGUU OH RNA, syn 23 AS G26 AAAGUGUGUGUGUGUGUGUGUGUCGU OHRNA, syn 24 AS G25 AAAGUGUGUGUGUGUGUGUGUGUCG OH RNA, syn 25 AS G24 + 2AAAAAAGUGUGUGUGUGUGUGUGUGUC OH RNA, syn 26 AS G24 + AAAAAGUGUGUGUGUGUGUGUGUGUC OH RNA, syn 27 AS G24 AAAGUGUGUGUGUGUGUGUGUGUCOH RNA, syn 28 AS G23 AAGUGUGUGUGUGUGUGUGUGUC OH RNA, syn 29 AS G21GUGUGUGUGUGUGUGUGUGUC OH RNA, syn 30 AS G20 UGUGUGUGUGUGUGUGUGUC OHRNA, syn 31 AS G19 GUGUGUGUGUGUGUGUGUC OH RNA, syn 32 AS G17GUGUGUGUGUGUGUGUC OH RNA, syn 33 AS G15 GUGUGUGUGUGUGUC OH RNA, syn 34AS G13 GUGUGUGUGUGUC OH RNA, syn 35 AS C26 AAAGUGUGUGUGUGUGUGUGUGUGGU OHRNA, syn 36 AS C24 AAAGUGUGUGUGUGUGUGUGUGUG OH RNA, syn 37 AS U26AAAGUGUGUGUGUGUGUGUGUGUAGU OH RNA, syn 38 AS U24 AAAGUGUGUGUGUGUGUGUGUGUOH RNA, syn 39 AS23 AAAGUGUGUGUGUGUGUGUGUGU OH RNA, syn 40 AS21AAAGUGUGUGUGUGUGUGUGU OH RNA, syn 41 AS19 AAAGUGUGUGUGUGUGUGU OHRNA, syn 42 IVT2 GACGACGACGACGACGACGACGACGACGAC 3P RNA, ivt 43 dAdT(AT)₂₀₀₋₄₀₀₀ P DNA, syn (syn: synthetic; ivt: in vitro transcribed)

As shown in FIGS. 4A, 5A and 6A, a minimal length of 21 nucleotides wasrequired for a double-stranded 3pRNA oligonucleotide to induce IFN-αfrom monocytes. Furthermore, the highest IFN-α-inducing activity wasseen when the double-stranded 3pRNA oligonucleotide had a blunt end atthe same end bearing the 5′ triphosphate. Blunt end formation at thenon-triphosphate end appears not to be preferred as double-strandedoligonucleotides bearing a 1 nt 3′ overhang at the non-triphosphate endhad higher IFN-α-inducing activity than those having a blunt end at thenon-triphosphate end (FIGS. 5A and 6, compare 3P-A+AS A23 and 3P-A+ASA24, or 3P-G+AS G23 and 3P-G+AS G24). Moreover, dsRNA oligonucleotideswith an A at the 5′ end bearing the 5′ triphosphate were more potent ininducing IFN-α than those with a G or U at the same position; dsRNAoligonucleotides with a C at the 5′ end bearing the 5′ triphosphate wasthe least potent. Similar results were obtained with PDC-depleted PBMCsand chloroquine-treated PBMCs (FIG. 4-6, B & C).

In contrast, double-stranded oligonucleotides bearing a 5′ monophosphatewere not effective at inducing IFN-α, regardless of the end structures(FIG. 6).

These data suggest 5′ triphosphate is required for RIG-I recognition.Furthermore, blunt end is a molecular signature recognized by RIG-I; itaugments the potency of a synthetic double-stranded RNA oligonucleotidebearing 5′ triphosphate at the same end in inducing IFN-α via the RIG-Ipathway.

Example 4 Single-Stranded RNA Transcripts can be Generated by In VitroTranscription

Both synthetic dsRNA bearing 5′ triphosphate and in vitro transcribedssRNA have been shown to be able to activate RIG-I^(15, 25). The presentinventors found that double-stranded configuration is required for RIG-Iactivation¹⁹. It was hypothesized that ssRNA obtained by in vitrotranscription was capable of activating RIG-I probably due to thepresence of aberrant RNA transcripts which had a double-strandedconfiguration.

Indeed, when ssRNA was transcribed in vitro in the presence of all 4NTP's (i.e., ATP, UTP, GTP, CTP) and run on a urea polyacrylamide gel,two bands were observed, indicating the presence double-stranded species(FIG. 7C, sample 4, “ivt3P-G_ACA”).

TABLE 4 Sequence of RNA oligonucleotides. name sequence type SEQ ID NO3P-G 5′-pppGACACACACACACACACACACUUU-3′ RNA, synthetic 9 AS-G215′-OHGUGUGUGUGUGUGUGUGUGUC-3′ RNA, synthetic 30 inv3P-G_ACA5′-pppGACACACACACACACACACACACA-3′ RNA, in vitro 44 transcribed

Subsequently, in vitro transcription was carried out in the absence ofUTP. Surprisingly, the upper band disappeared from the gel and thetranscript did not induce any IFN-α induction from purified primaryhuman monocytes (FIG. 7A-C, sample 5, “ivt3P-G_ACA-U”).

The addition of a synthetic complementary strand (AS G21) to such an invitro transcribed single-strand RNA oligonucleotide (ivt3P-G_ACA-U)which by itself has no IFN-inducing activity restored the IFN-inducingactivity (FIG. 1A-C, sample 6, “ivt3P-G_ACA-U+AS G21”).

This result suggests that it is possible to obtain an ssRNA withoutdouble strand formation, and without IFN-inducing activity from in vitrotranscription. Such an in vitro transcribed ssRNA can become an activeRIG-I ligand only upon double strand formation with a complementarystrand.

Example 5 The Effect of 2′-O-methylation on the IFN-α-Inducing Activityof a Blunt Ended RNA Olignucleotide Bearing 5′ Triphosphate isPosition-Dependent

Monocytes were purified from healthy donors and stimulated with 0.8μg/ml of the indicated double-stranded oligonucleotides (FIG. 8)complexed with 2 μl of Lipofectamine. The strand with the 5′triphosphate-bearing 5′ A (i.e., 3P-A) is hereinafter referred to as the“sense strand” and its complementary strand (AS A24 with and withoutmodifications), the “antisense strand”.

2′-O-methylation of U at various positions, positions 2, 4, 12 and 20from the 3′ end, in the antisense strand decreased the IFN-α-inducingactivity of the double-stranded 3P oligonucleotide (FIG. 8). Theobservation appears consistent with previous report that nucleosidemodifications which occur during eukaryotic post-transcriptional RNAprocessing abrogated the IFN-inducing activity of RNAolignucleotides^(15, 19). The activity-decreasing effect was most thepronounced when the 2′-O-methylation occurred at position 2 from the 3′end of the antisense strand.

Surprisingly, the most 3′ U of the antisense strand was 2′-O-methylated,the IFN-inducing activity of the double-stranded olignucleotide was notonly not reduced, but enhanced approximately 20% (FIG. 8).

These results suggest the possibility of modulating the IFN-inducingactivity of a 3P oligonucleotide by 2′-O-methylation at specificpositions. Whereas the IFN-inducing activity of a 3P olignucleotide maybe enhanced by 2′-O-methylation of a most 3′ nucleotide which base pairswith a most 5′ ribonucleotide bearing a 5′ triphosphate at a blunt end,the IFN-inducing activity may be reduced by 2′-O-methylation of anyother nucleotide, especially the second most 3′ nucleotide which is just5′ of the most 3′ nucleotide which base pairs with a most 5′ribonucleotide bearing a 5′ triphosphate at a blunt end.

Example 6 Molecular Motifs Recognized by and Activating RIG-I Materialsand Methods Chemical Synthesis of Triphosphate Oligoribonucleotides

Oligoribonucleotides containing a free 5′-OH terminus were synthesizedon an ABI 392 synthesizer using commercial 5′-Silyl 2′ ACE protectedamidites from Dharmacon. Solid phase triphosphorylation was performedusing an improved version of the protocol developed by Ludwig andEckstein²⁷. End products were precipitated as sodium salt from Ethanol.MALDI-ToF analysis was performed by Metabion (Martinsried, Germany).

Monophosphate RNA, Non-Modified RNA and In Vitro Transcribed RNA

Monophosphate RNA and non-modified RNA oligoribonucleotides (ORN) weresynthesized by commercial providers (Metabion, Martinsried, Germany andBiomers, Ulm, Germany, respectively). The sequences are listed inTable 1. Ivt3P-G and Ivt3P-Gaca were generated by in vitro transcription(IVT) with a commercial In vitro T7-Transcription Kit (Epicentre). Forgeneration of DNA template dependent in vitro transcribed RNA, theT7-promoter region CAGTAATAGGACTCACTATAG was hybridized with thepromoter+template strand (Ivt3P-G: 3′-GTC ATT ATG CTG AGT GAT ATC TGTGTG TGT GTG TGT GTG TGA AA-5′; Ivt3P-Gaca: 3′-GTC ATT ATG CTG AGT GATATC TGT GTG TGT GTG TGT GTG TGT GT-5′; IVT2: 3′-GTC ATT ATG CTG AGT GATATC TGC TGC TGC TGC TGC TGC TGC TGC TGC TG-5′) and directly used as atemplate for the in vitro transcription reaction. For generation ofivt3P-G w/o U and ivt3P-Gaca w/o U the in vitro transcription wasperformed in the absence of UTP.

Cell Culture

Human PBMCs were isolated from whole human blood of healthy, voluntarydonors by Ficoll-Hypaque density gradient centrifugation (BiochromBerlin, Germany). Plasmacytoid dendritic cells (PDC) were positivelydepleted using magnetically labelled anti-CD304 antibody (MiltenyiBiotec). Untouched monocytes were obtained by negative depletion fromPBMCs according to the manufacturers instructions (Human MonocyteIsolation Kit II, Miltenyi Biotec). Viability of all cells was above95%, as determined by trypan blue exclusion. If not indicated otherwise,400,000 cells (PBMCs) or 200,000 cells (monocytes) were cultured in96-well plates for stimulation experiments. Cells were kept in RPMI 1640containing 10% FCS, 1.5 mM L-glutamine, 100 U/ml penicillin andstreptomycin 100 μg/ml. All compounds were tested for endotoxincontamination prior to use.

Detection of Cytokines

The amount of IFN-a production was determined using the IFN-a module setfrom Bender MedSystems (Vienna, Austria). The ELISA assay was performedaccording to the manufacturer's protocol. The concentration of cytokineswas determined by the standard curve obtained using known amounts ofrecombinant cytokines.

Flow Cytometry

Cell purity was assessed by FACS analysis of cell surface antigens usinga FACS LSRII (BD Biosciences, Heidelberg, Germany). Human monocytes werestained with antibody against CD14-FITC or CD14-APC and cell purity wasbetween 83% and 99%. Human PDCs were positively labelled with antibodyagainst CD123-PE, HLA-DR-PerCp and negatively for CD11c-APC and acocktail to lineage markers (FITC). Antibodies were purchased from BDPharMingen. Data analysis was performed on viable cells using CellQuest(BD Biosciences) and Flowjo (Treestar).

Protein Purification and Analysis

(His₆)-Flag-tagged RIG-I (HF-RIG-I) was transiently overexpressed in293T cells and lysed in a CHAPS containing lysis buffer (150 mM NaCl, 50mM Tris/HCl pH7.4, 2 mM MgCl₂, 1 mM DTT, 1% CHAPS) including proteaseinhibitor cocktail (Roche). The lysate was incubated over night at 4° C.with ANTI-FLAG beads (Sigma). Anti-FLAG beads were washed subsequentlywith lysis buffer and high salt wash buffer (300 mM NaCl, 50 mM Tris/HClpH7.4, 5 mM MgCl₂, 1 mM DTT, 0.1% CHAPS). RIG-I-FLAG was eluted byaddition of FLAG-peptide (300 ug/ml) solution to the beads. Purity ofrecombinant RIG-I was determined by SDS-PAGE separation and subsequentCoomassie blue stain (FIG. 4G).

ATPase Assay

The ATPase assay was performed in assay buffer (50 mM KCl, 55 mM HEPES(pH 7.0) 3 mM MgCl₂, 0.5 mM DTT, 0.1 mM ATP). In order to calculateEC50, the RNA was titrated in a range from 6 fM to 4 μM. After 30 min ofincubation at 37° C., occurrence of ADP was measured using a verysensitive FRET based competitive immunoassay (HTRF® Transcreener™ ADP,Cisbio, Bedford, USA) according to the manufacturers protocol. FRET wasmeasured using an EnVision® Multilabel Reader (PerkinElmer, Waltham,USA). In this assay, inhibition of FRET correlates with theconcentration of ADP generated by ATPase activity of RIG-I. ADPconcentrations were calculated from an ADP/ATP titration curve accordingto the manufacturers protocol.

AlphaScreen RIG-I-Binding Assay

The binding affinity of RNA for (His₆)FLAG-tagged RIG-I (HF-RIG-I) wasdetermined as described^(31, 32) by an amplified luminescent proximityhomogenous assay (AlphaScreen; Perkin Elmer). In this assay purifiedHF-RIG-I was incubated with increasing concentrations of biotinylatedRNA for 1 hour at 37° C. in buffer (50 mM Tris/pH7.4, 100 mM NaCl, 0.01%Tween20, 0.1% BSA) and subsequently incubated for 30 min at 25° C. withHF-RIG-I-binding Nickel Chelate acceptor beads (Perkin-Elmer) andbiotin-RNA-binding Streptavidine donor beads (Perkin Elmer). The donorbead contains the photosensitizer phtalocyanine, which converts ambientoxygen into a ‘singlet’ oxygen after illumination with a 680-nm laserlight. During the 4-s lifetime, the ‘singlet’ oxygen can diffuse up to200 nm and activate a thioxene derivative on the acceptor bead that isbrought into proximity by interaction of the test molecules bound to thebeads. The resulting chemiluminescence with subsequent activation of afluorochrome (contained within the same bead) emitting in the range of520-620 nm correlates with the number and proximity of associated beadswhich is inversely correlated with the dissociation constant of donor(biotin-RNA) and acceptor (HF-RIG-I). The assay was performed in wellsof 384-well plates (Proxiplate; Perkin-Elmer). Plates were analyzed foremitted fluorescence with a multilabel reader (Envision; Perkin Elmer).

Results

A 24mer RNA oligonucleotide with 5′-G (3P-G) was designed for whichself-complementarity and thus secondary structure formation (intra- orintermolecular double strand formation) was predicted to be absent (seeTable 5). A triphosphate group was covalently attached to the 5′end ofthe corresponding synthetic oligonucleotide by using a previouslyestablished method²⁷. Purity of RNA oligonucleotides was confirmed usingHPLC and MALDI-ToF (FIG. 9A-C). The same sequence (ivt3P-G) as well as apositive control oligonucleotide (IVT2, 30mer, Table 5) were generatedby in vitro transcription. The RIG-I activity of RNA oligonucleotideswas examined in primary human monocytes, a well-established assay forRIG-I activation¹⁵.

TABLE 5 Oligonucleotide Sequences (5′->3′) Name Sequence 5′ end TypeSEQ ID NO: 3P-A A ACACACACACACACACACACUUU 3P RNA, syn 8 ivt3P-G GACACACACACACACACACACUUU 3P RNA, ivt 9 ivt3P-Gaca GACACACACACACACACACACACA 3P RNA, ivt 44 3P-G G ACACACACACACACACACACUUU 3PRNA, syn 9 3P-C C ACACACACACACACACACACUUU 3P RNA, syn 10 3P-U UACACACACACACACACACACUUU 3P RNA, syn 11 HO-A A ACACACACACACACACACACUUU OHRNA, syn 8 P-A A ACACACACACACACACACACUUU P RNA, syn 8 AS A34AAAGUGUGUGUGUGUGUGUGUGUUGUG OH RNA, syn 45 GUGUGU AS A26AAAGUGUGUGUGUGUGUGUGUGUUGU OH RNA, syn 12 AS A25AAAGUGUGUGUGUGUGUGUGUGUUG OH RNA, syn 13 AS A24 + 2AAAAAAGUGUGUGUGUGUGUGUGUGUU OH RNA, syn 14 AS A24 + AAAAAGUGUGUGUGUGUGUGUGUGUU OH RNA, syn 15 AS A24 AAAGUGUGUGUGUGUGUGUGUGUUOH* RNA, syn 16 AS A24P AAAGUGUGUGUGUGUGUGUGUGUU OH** RNA, syn 16 AS A23AAGUGUGUGUGUGUGUGUGUGUU OH RNA, syn 17 AS A21 GUGUGUGUGUGUGUGUGUGUU OHRNA, syn 18 AS A20 UGUGUGUGUGUGUGUGUGUU OH* RNA, syn 19 AS A19GUGUGUGUGUGUGUGUGUU OH RNA, syn 20 AS G26 AAAGUGUGUGUGUGUGUGUGUGUCGU OHRNA, syn 24 AS G25 AAAGUGUGUGUGUGUGUGUGUGUCG OH RNA, syn 25 AS G24 + 2AAAAAAGUGUGUGUGUGUGUGUGUGUC OH RNA, syn 26 AS G24 + AAAAAGUGUGUGUGUGUGUGUGUGUC OH RNA, syn 27 AS G24 AAAGUGUGUGUGUGUGUGUGUGUCOH RNA, syn 28 AS G23 AAGUGUGUGUGUGUGUGUGUGUC OH RNA, syn 29 AS G21GUGUGUGUGUGUGUGUGUGUC OH RNA, syn 30 AS G20 UGUGUGUGUGUGUGUGUGUC OHRNA, syn 31 AS G19 GUGUGUGUGUGUGUGUGUC OH RNA, syn 32 AS G17GUGUGUGUGUGUGUGUC OH RNA, syn 33 AS G15 GUGUGUGUGUGUGUC OH RNA, syn 34AS G13 GUGUGUGUGUGUC OH RNA, syn 35 AS C26 AAAGUGUGUGUGUGUGUGUGUGUGGU OHRNA, syn 36 AS C24 AAAGUGUGUGUGUGUGUGUGUGUG OH RNA, syn 37 AS U26AAAGUGUGUGUGUGUGUGUGUGUAGU OH RNA, syn 38 AS U24AAAGUGUGUGUGUGUGUGUGUGUA OH RNA, syn 39 AS23 AAAGUGUGUGUGUGUGUGUGUGU OH*RNA, syn 40 AS21 AAAGUGUGUGUGUGUGUGUGU OH RNA, syn 41 AS19AAAGUGUGUGUGUGUGUGU OH RNA, syn 42 IVT2 GACGACGACGACGACGACGACGACGAC 3PRNA, ivt 43 GAC dAdT (AT)₂₀₀₋₄₀₀₀ P DNA ASGFP2 AAGAUGAACUUCAGGGUCAGCGUCOH RNA, syn 46 ASGFP2 3′23 AAGAUGAACUUCAGGGUCAGCGU OH RNA, syn 47ASGFP2 3′21 AAGAUGAACUUCAGGGUCAGC OH RNA, syn 48 ASGFP2 3′19AAGAUGAACUUCAGGGUCA OH RNA, syn 49 ASGFP2 5′21 AUGAACUUCAGGGUCAGCGUC OHRNA, syn 50 ASGFP2 5′19 GAACUUCAGGGUCAGCGUC OH RNA, syn 51 3P-GFP1GGGGCUGACCCUGAAGUUCAUCUU 3P RNA, syn 52 3P-GFP2 GACGCUGACCCUGAAGUUCAUCUU3P RNA, syn 53 3P-GFP3 GGGGCGCUGACGCCCUGAAGUUCA 3P RNA, syn 54 TAK P25AAACUGAAAGGGAGAAGUGAAAGUG P RNA, syn 55 TAK 25PAAACUGAAAGGGAGAAGUGAAAGUGAG OH** RNA, syn 56 TAK 25AAACUGAAAGGGAGAAGUGAAAGUG OH RNA, syn 57 TAK 25cCACUUUCACUUCUCCCUUUCAGUUU OH RNA, syn 58 3P = triphosphate, P =monophosphate, ivt = in vitro transription; syn = synthetic *Oligos usedfor alpha screen were labelled with biotin at the 5′ end. **AS A24P andTAK 25P were monophosphorylated at the 3′end.

As expected, the in vitro transcribed form of 3P-G and the positivecontrol sequence IVT2 induced IFN-α in monocytes. Unexpectedly,synthetic 3P-G showed no IFN-α induction (FIG. 9D). Polyacrylamide gelanalysis revealed that ivt3P-G presented as two major bands one of whichran slower than the single band of synthetic 3P-G (FIG. 9E, lane 5versus lane 1). Since synthetic 3P-G is molecularly defined, ivt3P-Gforms slower running bands either due to self complementarity or due tohigher molecular weight. Self complementarity is unlikely to be presentgiven the sequence that we used. However, the higher molecular weightcould result from RNA template dependent RNA transcription that leads tocomplementary side products and to double-stranded RNA products from IVTreactions which where originally designed to be single stranded. Indeed,the addition of a fully synthetic complementary single strand (notcontaining a triphosphate group, AS G24) to 3P-G (3P-G+AS G24) led tofull RIG-I ligand activity (FIG. 9D).

We then changed the sequence of 3P-G to 3P-Gaca by replacing the three3′UUU to 3′ACA (see FIG. 9F right panel). The in vitro transcription of3P-Gaca requires only three nucleotides G, C and A but not U in the invitro reaction mix. Therefore, double strand formation can only occur inthe presence of U. Consistent with the results obtained by using definedsynthetic RNAs, we found that ivt3P-Gaca strongly induced IFN-α, whileivt3P-Gaca w/o U (absence of U in reaction mix, no double strandexpected) showed no IFN-α induction (FIG. 9F). The addition of the 21mercomplementary strand (AS G21) restored IFN-α inducing activity. The lackof double strand formation of ivt3P-Gaca w/o U was confirmed using gelanalysis (FIG. 9F)

Next the length of the strand complementary to 3P-G (AS G24) wasdecreased from 24 down to 13 nucleotides (3P-G with complementary AS G24to AS G13, see FIG. 10A, and Table 5). We found that with the sequence3P-G, AS G21 was the minimal tolerated length of a complementary strand(FIG. 10A). AS G23 together with 3P-G (one nucleotide 3′ overhang at thenon-triphosphate end) consistently showed higher activity than AS G24(no overhang at the non-triphosphate end); the same was seen for AS A23and AS A24 with 3P-A (FIG. 10B), suggesting that blunt end formation atthe non-triphosphate end is not preferred.

To analyse the contribution of the 5′-nucleoside we compared the RIG-Iligand activity of 3P-G to the other three synthetic variants (3P-A,3P-C, 3P-U). A preference for a 5′-adenosine compared to 5′-guanosinewas observed (FIGS. 10C and 10D). Furthermore, elongation of thecomplementary strand at the non-triphosphate end for both 3P-G and 3P-Adid not reduce but rather increased the IFN-α inducing activity (FIG.11A).

Unlike the non-triphosphate end, elongation at the triphosphate endreduced RIG-I ligand activity (FIGS. 11B and 13). RIG-I ligand activitywas specifically sensitive to shortening of the complementary strandresulting in a 5′overhang at the triphosphate end (3P-G+AS 23, 3P-G+AS21, 3P-G+AS19, FIG. 11C). Identical results were seen with an unrelatedRNA sequence (GFP2, see FIG. 14). The comparison of three relatedsequences, 3P-GFP1, 3P-GFP2 and 3P-GFP3, suggested that stem-loopsecondary structure formation in a single strand RNA oligonucleotide isnot sufficient for RIG-I activation (FIG. 14, sequences see Table 5).

Next we compared synthetic 5′ monophosphate single strand RNA (P-A) tosynthetic 5′triphosphate single strand RNA (3P-A) and varied the lengthof the complementary strand in order to study the contribution of bluntend and the length of the double strand portion (FIG. 11D). Compared tothe 5′triphosphate version of the same sequence we found no considerableIFN-α induction by 5′ monophosphate blunt end double strand RNA (P-A+ASA24). A one nucleotide 3′ overhang at the monophosphate end (P-A+AS A25)or a one nucleotide 3′overhang of the monophosphate strand (P-A+AS A23)(FIG. 11D), or shortening the complementary strand down to 21nucleotides (P-A+AS A21) did not increase RIG-I activity (data notshown). The same was seen for the RNA sequences of Takahasi andcolleagues (FIG. 15)²⁴.

We analysed the direct interaction of purified human RIG-I proteinisolated from HEK293T cells with different single strand and doublestrand RNA ligands. Single strand RNA (all open symbols) irrespectivelyof 5′ triphosphate or 5′monophosphate did not induce ATPase activity(FIG. 12A). Double strand RNA molecules (all black symbols) showed anEC50 in the range of 15 nM to 600 nM depending on the composition of thedouble strand and the configuration of the 5′ end (FIG. 12A). Doublestrand RNA with 5′ monophosphate and without 5′ phosphate (P-A+AS A24,HO-A+AS A24) showed a 35- and 20-fold higher EC50 (lower ATPaseactivity) than double strand RNA with a 5′triphosphate (FIG. 12A). The5′triphosphate double strand RNA molecules which induced substantialamounts of IFN-α in monocytes (3P-A+AS A24, 3P-A+AS A23, 3P-A+AS A21,see FIG. 13) reached their EC50 at 20- to 150-fold lower concentrationsthan dsRNA ligands that weakly induced IFN-α (3P-A+AS A34, 3P-A+AS23,3P-A+AS21, 3P-A+AS19, 3P-A+ASA19) (FIG. 12B, compare to FIGS. 13A and13B). The ATPase activities of different 5′-triphosphate RNAs withdifferent 5′bases (3P-A+AS A24, 3P-G+AS G24, 3P-U+AS U24, 3P-C+AS C24,FIG. 12C) reflected the observed IFN-α inducing activity (A=G=U>C,compare FIG. 10A). These data demonstrate that the IFN-α inducingactivity of RNA RIG-I ligands correlates with ATPase activity.

Using a homogenous ligand interaction assay we analysed the affinity ofdifferent RNA molecules to RIG-I, we found that binding of RNA to RIG-Istrictly depended on the presence of a triphosphate at the 5′ end (FIGS.12D and 12E). The dissociation constant of 5′-triphosphate RNA (3P-A+ASA24) was approximately 4 nM. The Kd(app) of corresponding non-modified,5′ monophosphate RNA or dephosphorylated 3P-RNA (HO-A+AS A24, P-A+ASA24, 3P-A+AS A24 CIAP) was above the detection limit of this assay butat least 1000-fold higher than the Kd(app) of 5′triphosphate doublestrand RNA (FIGS. 12D, E & F). Consistent with IFN-α inducing activityin monocytes, the magnitude of binding of IFN-α inducing (3P-A+AS A24)and of non-IFN-α-inducing (3P-A+AS23, 3P-A+AS A20, compare FIG. 12C andFIG. 13) 5′-triphosphate RNA to RIG-I differed 4- to 5-fold (FIG. 12E).

Together these results demonstrate that i) 5′triphosphate single strandRNA is not sufficient for RIG-I activation, ii) the recognition of5′triphosphate requires a double strand spanning at least 21 nucleotidesencompassing the 5′ nucleotide carrying the triphosphate, iii) a 3′overhang at the 5′triphosphate end decreases and any 5′ overhang at the5′triphosphate end abolishes the activity, and iv) adenosine is thepreferred nucleoside carrying the triphosphate. Furthermore, thereplacement of 5′ triphosphate by 5′ monophosphate without results in asubstantial loss of IFN-α inducing activity.

It was reported that double strand RNA is not only present in doublestrand RNA viruses but substantial amounts of cytosolic double strandRNA are also produced during the replicative life cycle of positivesingle strand RNA viruses³³. In agreement with the requirement of doublestrand RNA for RIG-I recognition, double strand and positive singlestrand RNA viruses indeed present ligands for RIG-I^(10, 34). However,at first sight, this seemed less clear for RIG-1-mediated detection ofnegative single strand RNA viruses^(10, 34) for which no double strandRNA can be detected^(25, 33) but still viral genomic single strand RNAactivates RIG-I^(15,25). However, the antibody used to demonstrate theabsence of double strand RNA^(25, 33) is limited to the detection ofdouble strand RNA longer than 40 bases³⁵. Performing a careful analysisof sequence data we noted that genomes of negative strand viruses knownto activate RIG-I contain 5′ and 3′ sequences that form a short doublestrand with a perfect blunt end and a 5′ adenosine carrying thetriphosphate group (FIG. 16). Such panhandle structures³⁶ serve as a RNAtranscription initiation site for the viral RNA polymerase complex andwere extensively studied for the influenza virus³⁷.

Example 7 Bcl-2 Silencing and Anti-Tumor Activity Material andMethods 1. Cell Lines

Murine B16 melanoma cells (H-2^(b)), C26 adenocarcinoma cells (H-2^(d)),NIH-3T3 fibroblasts and primary murine embryonal fibroblasts (MEF) werecultivated in Dulbecco's modified Eagle's medium (Biochrom, Berlin,Germany) supplemented with 10% heat-inactivated fetal calf serum (FCS,Invitrogen Life Technologies), 2 mM L-glutamine, 100 U ml⁻¹ penicillin,100 μg ml⁻¹ streptomycin and 10 mM β-mercaptoethanol (all fromSigma-Aldrich). The human melanoma cell line 1205 Lu (M. Herlyn, WistarInstitute, Philadelphia, Pa., USA) was cultured in MCDB153 (Sigma) with20% Leibovitz's L-15 (PAA Laboratories), 2% FCS (PAA Laboratories), 1.68mM CaCl₂ (Sigma) and 5 μg ml⁻¹ insulin (Sigma).

2. Culture of Primary Cells

Murine primary cells were cultivated in VLE RPMI 1640 (Biochrom)supplemented with 10% FCS, 3 mM L-Glutamine, 100 μg streptomycin, 100U/ml penicillin and 10 mM β-mercaptoethanol. Plasmacytoid DC (pDC) fromFlt3-ligand-induced (Flt3-L) bone marrow cultures were sorted with B220microbeads (Miltenyi Biotec). Conventional dendritic cells (cDC) weregenerated as described¹⁵. For some experiments B cells were isolatedfrom spleens of wild-type mice by MACS using CD19 microbeads (MiltenyBiotec). Untouched NK cells and T cells were sorted from spleens usingthe NK cell isolation and the CD4 T Cell Isolation Kit (Milteny Biotec).Viability of all cells was above 95%, as determined by trypan blueexclusion and purity was >90% as analyzed by FACS.

3. RNAs

Chemically synthesized RNA oligonucleotides were purchased fromEurogentec (Leiden, Belgium) or MWG-BIOTECH AG (Ebersberg, Germany). Fora detailed list of all chemically synthesized RNA oligonucleotides usedfor this experiment see Table 7. In some experiments single-strandedpolyriboadenosinic acid (PolyA) or non-silencing control siRNAs wereused as control-RNAs (indicated in Table 7). In vitro transcribed RNAswere synthesized as described¹⁵. For a detailed list of all in vitrotranscription templates see Table 8.

TABLE 7 Chemically synthesized siRNA sequences Name Type Sequence 5′->3Murine Bcl-2 2.1 sense RNA AUGCCUUUGUGGAACUAUA Murine Bcl-2 2.1 anti-RNA UAUAGUUCCACAAAGGCAU sense Murine Bcl-2 2.2 sense RNAGCAUGCGACCUCUGUUUGA Murine Bcl-2 2.2 anti- RNA UCAAACAGAGGUCGCAUGC senseMurine Bcl-2 2.3 sense RNA GGAUGACUGAGUACCUGAA Murine Bcl-2 2.3 anti-RNA UUCAGGUACUCAGUCAUCC sense PolyA (used in FIG. 18a-d; RNAAAAAAAAAAAAAAAAAAAA FIG. 20b-d; FIG. 20f) Murine RIG-I sense RNAGAAGCGUCUUCUAAUAAUU Murine RIG-I anti-sense RNA AAUUAUUAGAAGACGCUUCControl siRNAsense (used RNA UUCUCCGAACGUGUCACGUin FIG. 17 a, b, c; FIG. 19 a-c and FIG. 19 e-g, FIG. 20a and 20e; FIG.21a-e; FIG. 22a-e) Control siRNA anti-sense RNA ACGUGACACGUUCGGAGAA(see above) Murine Bcl-2 2.4 sense RNA GGAGAACAGGGUAUGAUAAMurine Bcl-2 2.4 anti- RNA CCUCUUGUCCCAUACUAUU senseHuman Bcl-2 h2.2 sense RNA GCAUGCGGCCUCUGUUUGA Human Bcl-2 h2.2 anti-RNA CGUACGCCGGAGACAAACU sense IFNAR sense RNA TGGAAGCCGTTCAGATAAAIFNAR anti-sense RNA TTTATCTGAACGGCTTCCA

TABLE 8 DNA-oligonucleotides (templates) for in vitro transcription NameType Sequence 5′->3 Murine Bcl-2 2.2 sense DNATCAAACAGAGGTCGCATGCCTATAGTGAGTCG Murine Bcl-2 2.2 anti-sense DNAGCATGCGACCTCTGTTTGACTATAGTGAGTCG GC sense DNAGGCGCCCCGCCGCGCCCCGCTATAGTGAGTCG GC anti-sense DNAGCGGGGCGCGGCGGGGCGCCTATAGTGAGTCG Murine Bcl-2 2.4 sense DNATTATCATACCCTGTTCTCCCTATAGTGAGTCG Murine Bcl-2 2.4 anti-sense DNAGGAGAACAGGGTATGATAACTATAGTGAGTCG Human Bcl-2 h2.2 sense DNATCAAACAGAGGCCGCATGCCTATAGTGAGTCG Human Bcl-2 h2.2 anti-sense DNAGCATGCGGCCTCTGTTTGACTATAGTGAGTCG Murine Bcl-2 mismatch sense DNATCAAACAGTCCTCGCATGCCTATAGTGAGTCG (3p-MM) Murine BcL-2 mismatch (3p-MM)DNA GCATGCGAGGACTGTTTGACTATAGTGAGTCG anti-sense

4. Transfection of RNA In Vitro

We transfected melanoma cells at a conflueny of 50-70% for 24 h withRNAs (1 μg ml⁻¹), using Lipofectamine 2000 or Lipofectamine RNAiMAX(both Invitrogen) according to the manufacturer's protocol. Wetransfected DC and immune cell subsets with 200 ng of nucleic acid with0.5 μl of Lipofectamine in a volume of 200 μl.

5. Plasmids

IFN-β-Luc reporter plasmids, wild-type pPME-myc NS3-4A (NS3-4A),pPME-myc MutNS3-4A (NS3-4A*; containing an inactivating Serin 139 to Alamutation) were kindly provided by T. Maniatis and J. Chen. RIG-I and theempty control vector were kindly provided by T. Fujita¹¹. Therenilla-luciferase transfection efficiency vector (phRLTK) was purchasedfrom Promega. cDNA encoding WT murine Bcl-2 (mBcl-2/pcDNA) was providedby Christoph Borner (Institute of Molecular Medicine and Cell Research,Albert-Ludwigs-University of Freiburg, Germany)

6. In Vitro and In Vivo RACE

We purified total RNA of B16 cells (in vitro) or from pooled metastaticlung tissue using Tryzol reagent (Invitrogen) and the RNeasypurification procedure (QIAGEN). 5 μg of RNA from pooled samples wasdirectly ligated to GeneRacer adaptor[AP1] (Invitrogen;5′-CGACUGGAGCACGAGGACACUGACAUGGACUGAAGGAGUAGAAA). Ligated RNA wasreverse transcribed using a gene-specific primer (Table 9). To detectcleavage product, we performed 2 rounds of consecutive PCR using primerscomplementary to the RNA adaptor and mBcl2 mRNA (GR5′ and Rev 1 or Rev 2for the 1^(st) PCR round; GRN5′ and RevN—for the nested PCR). For adetailed list of all the primers used for 5′-RACE see Table 9. Weconfirmed the identity of specific cleavage products by cloning of thePCR product and sequencing of individual clones.

TABLE 9 Primers used for 5′-RACE Name Application Sequence 5′-3′ cDNAcDNA synthesis GTTCATCTGAAGTTTCCAGCCTTTG GR 5′5′RACE product forward per primer, CGACTGGAGCACGAGGACACTGA 1st roundGRN 5′ 5′RACE product forward per primer, GGACACTGACATGGACTGAAGGAGTAnested round Rev. 1 5′RACE product reverse per primer,TCCCTTTGGCAGTAAATAGCTGATTCGACCAT 1st round, in vivo samples assay Rev. 25′RACE product reverse per primer, AAGTCCCTTCTCCAGTCCATGGAAGACCAG1st round, in vitro samples assay RevN5′RACE product reverse per primer, CTTTGGCAGTAAATAGCTGATTCGACCATTTGCnested round

7. Western Blotting

We lysed cells in a buffer containing 50 mM Tris; pH 7.4, 0.25M NaCl, 1mM EDTA, 0.1% Triton X-100, 0.1 mM EGTA, 5 mM Na₃VO₄, 50 mM NaF andprotease inhibitors (Complete, Mini, EDTA-free, Roche), separatedsamples by SDS-PAGE and transferred them to a nitrocellulose membrane(Amersham-Biosciences) by semi-dry electroblotting. Antibodies specificfor RIG-I, Bcl-2 (Santa Cruz, sc-7382), Mcl-1, Bcl-xL, Bim and Puma (allCell Signaling Technology) were incubated at 4° C. over night anddetected via a peroxidase-conjugated anti-rat or anti-rabbit secondaryantibody (Amersham-Biosciences). Bands were visualized bychemiluminescence (ECL Kit; Amersham-Biosciences).

8. Mice and In Vivo Treatment with RNAs

RIG-I-, MDA-5-, TLR7-, IFNAR-deficient mice and CD11c-DTR mice wereestablished as described^(3,10,55,56). The TLR7- and IFNAR-deficientmice used for tumor challenge experiments were crossed into the C57BL/6genetic background for at least 10 generations. HGF/CDK4^(R24C) micewere bred as described⁵⁷. Mice were treated intravenously with RNAsafter complexation with jetPEI according to the manufacturer's protocol.Briefly, for each mouse we mixed 10 μl of in vivo jetPEI with 50 μg ofnucleic acids (N:P ratio of 10/1) in a volume of 200 μl 5% glucosesolution and incubated for 15 min. We collected serum for cytokinemeasurements was after 6 h. For systemic DC depletion, we injectedCD11c-DTR transgenic mice intraperitoneally with 100 ng ofdiphteria-toxin (DT) in PBS (Sigma D-0564). We treated mice withjePEI-complexed RNAs 24 hr after DT-injection. We confirmed CD11c⁺depletion by flow cytometry.

9. Induction of B16 Melanoma Lung Metastases and Lymphocyte Depletion

We experimental induced lung metastases by injection of 4×10⁵ B16melanoma cells into the tail vein. For tumor treatment we adminstered 50μg of RNA complexed with jetPEI in a volume of 200 μl on day 3, 6 and 9after tumor cell challenge by retro-orbital or tail vein injection. 14days after challenge we counted the number of macroscopically visiblemelanoma metastases on the surface of the lungs. Depletion of NK cellsand CD8 T cells was performed as described⁵⁴.

10. Serial Transplantation of Primary Cutaneous Melanomas Derived fromHGF×CDK4^(R24C/R24C) Mice

We dissociated primary melanomas derived from carcinogen-treatedHGF×CDK4^(R24C/R24C) mice^(23,30), passed them through a nylon meshfilter (70 μl) and reinjected them in the flank of CDK4^(R24C/R24C)mice. We performed treatment experiments with groups of 5 miceintracutaneously injected with 10⁵ viable transplantedHGF×CDK4^(R24C/R24C) melanoma cells derived from one transplantedmelanoma in the fourth to sixth passage. We monitored tumor growthweekly by measuring the maximal two bisecting diameters (L=length andW=width) using a vernier sliding jaw caliper. We calculated tumor sizeaccording to the formula Volume=(L×W²)×0.5 and expressed it in mm³. Wesacrificed mice with tumors greater than 4000 mm³.

11. Statistical Analyses

We determined the statistical significance of differences by thetwo-tailed Student's t-test. For the analysis of the tumor experimentswe used the non-parametric Mann-Whitney U test to compare the meansbetween two groups. Statistical analysis was performed using SPSSsoftware (SPSS, Chicago, Ill.). P values<0.05 were consideredsignificant.

Anti-bcl-2 siRNA with 5′-Triphosphate Ends Reduces Formation of LungMetastases in B16 Melanoma

In order to test the feasibility of the 3p-siRNA approach for tumortherapy, we tested three synthetic siRNAs (anti-bcl-2.1, anti-bcl-2.2,anti-bcl-2.3) targeting different regions of murine Bcl-2 mRNA for theirability to downregulate Bcl-2 protein in B16 melanoma cells (FIG. 17 aleft panel and Table 7, below). The activity and the specificity ofBcl-2 downregulation was maintained when anti-Bcl-siRNA contained a5′-triphosphate (FIG. 17 a right panel and Table 8, OH-2.2 and 3p-2.2compared to 3p-GC and mismatch 3p-MM). Silencing of Bcl-2 by 3p-2.2 wasspecific since expression of the pro-survival Bcl-2 family members Mcl-1and Bcl-xL and of the pro-apoptotic BH3-only Bcl-2 family members Pumaand Bim was not inhibited (FIG. 23). Using RACE (Rapid Amplification ofcDNA Ends) technology and sequencing revealed that Bcl-2 silencinggenerated specific cleavage products confirming RNA interference (FIG.17 b).

Next we examined the anti-tumor activity of 3p-2.2 in the B16 melanomalung metastasis model in vivo. Mice were treated with RNA on days 3, 6and 9 after tumor cell inoculation and growth of lung metastases wasassessed on day 12 or 17. As shown in FIG. 17 c, OH-2.2 (gene silencingactivity but no RIG-I ligand activity expected) and the 3p-RNAoligonucleotides 3p-MM and 3p-GC (RIG-I ligand activity but no genesilencing activity expected) inhibited the growth of melanoma metastasesto a certain degree. However, 3p-2.2, which combines Bcl-2-specificgene-silencing and immunostimulatory properties, displayed significantlyenhanced therapeutic anti-tumor activity.

Type I IFN and NK Cells are Required for the Anti-Tumor Activity

Since 5′-triphosphate RNA is known to stimulate type I interferon byactivating RIG-I we sought to evaluate the contribution of type I IFN tothe anti-tumor effect. Experiments in type I IFN receptor knockout mice(IFNAR−/−) confirmed that the observed anti-tumor activity of 3p-2.2 invivo depended on intact type I IFN signaling (FIG. 18 a, compare leftand middle panel). We found that the number of metastases was stronglyreduced upon treatment with 3p-2.2 in TLR7-deficient mice suggestingthat TLR7 was not required for the anti-tumor activity of 3p-2.2 (FIG.18 a, right panel). This indicated that not TLR7- but ratherRIG-1-mediated 3p-2.2 recognition and type I IFN induction plays adominant role. Depletion studies demonstrated that the anti-tumoractivity of 3p-2.2 in the B16 melanoma model depended on NK cells butnot CD8 T cells (FIG. 18 b). Together these results confirm that bothgene silencing (since the 3p control 3p-GC is significantly less active)and RIG-I (but not TLR7) dependent immunity contribute to anti-tumoractivity of 3p-2-2 in the B16 melanoma model in vivo.

Innate Response and Apoptosis in Immune Cell Subsets and Tumor Cells InVitro

Next we studied stimulation of specific immune cell subsets in vitro.While in plasmacytoid dendritic cells TLR7 activation is sufficient toinduce the production of IFN-α, conventional dendritic cells (cDC)produce IFN-α in response to viral infection but not to TLR7 activation.3p-MM, 3p-GC and 3p-2.2 induced similar amounts of IFN-α in cDC, whileOH-2.2 was inactive (FIG. 19 a). 3p-RNA did not induce IFN-α in B cells,NK cells and T cells. Studies with dendritic cells isolated from micegenetically deficient for TLR7 or the cytosolic helicases MDA-5 or RIG-Iconfirmed that the induction of IFN-α in cDC by 3p-2.2 and 3p-GCdepended on RIG-I but not MDA-5 or TLR7 (FIG. 24). No induction ofapoptosis was observed in cDC or other lymphocyte subsets exposed to3p-2.2 (FIG. 19 b).

Since RIG-I is broadly expressed in many cell types, we examined directinduction of type I IFNs in B16 melanoma cells. 3p-2.2, 3p-MM or 3p-GCstimulated similar levels of IFN-β promoter reporter gene activity inB16 cells but did not respond to OH-2.2 or to phosphatase-treated 3p-2.2(FIG. 19 c). Resting B16 melanoma cells expressed little RIG-I; howeverRIG-I expression was strongly upregulated in the presence of exogenousIFN-β or 3p-2.2 (FIG. 19 d). B16 cells treated with 3p-2.2 or 3p-GC butnot OH-2.2 secreted the chemokine IP-10 and upregulated MHC class I.(FIGS. 25 a, and 25 b). Type I IFN induction in B16 tumor cells wasRIG-I dependent, since inhibition of RIG-I expression by RIG-1-specificsiRNA or overexpression of NS3-4A (encoding a serine protease ofhepatitis C virus cleaving IPS-1^(57,53), also known as Cardif, MAVS orVISA, a key signaling molecule of RIG-I) both eliminated the type I IFNresponse (FIG. 25 c, d). These data indicated that 3p-RNA is able toactivate type I IFN through Rig-I directly in tumor cells.

3p-2.2 siRNA was designed to promote the induction of apoptosis viasilencing of the anti-apoptotic protein Bcl-2. Indeed, 3p-2.2 stronglyinduced apoptosis in B16 melanoma cells (FIG. 19 e). Apoptosis inductionwith 3p-2.2 was substantially higher than with OH-2.2 alone andanti-bcl-2-siRNA reduced apoptosis induction by 3p-2.2 suggesting thatRIG-I contributed to apoptosis induction by 3p-2.2 (FIGS. 19 e and 19f). Furthermore, apoptosis induction by 3p-GC and 3p-2.2 was reduced inthe absence of IFNAR (FIG. 19 f; FIG. 25 e) suggesting that type I IFNsignaling is involved in sensitizing tumor cells to RIG-I. Unlike B16tumor cells, fibroblasts were not sensitive towards apoptosis inductionby silencing of Bcl-2 (OH-2.2) or activation of RIG-I (3p-GC) or thecombination of both (3p-2.2) (FIG. 19 g). Together with the lack ofapoptosis induction in immune cell subsets (FIG. 19 b) these resultsindicate that downregulation of Bcl-2 and activation of RIG-Ipreferentially lead to apoptosis of melanoma cells and suggest arelative tumor selectivity of this approach.

Analysis of Innate Immune Activation In Vivo

Next we studied 3p-2.2-induced innate immune responses in vivo. 3p-2.2induced systemic levels of IFN-α, IL-12p40 and IFN-γ (FIG. 20 a, FIG.26). IFN-α was largely derived from CD11c+ dendritic cells as evidencedby removal of this cell type in CD11c-DTR mice. The Th1 cytokineinduction by 3p-2.2 in vivo was dominated by RIG-I, with minorcontribution of TLR7 (FIG. 26). Cytokine production was dose-dependentand transient. Mice showed reduced counts of lymphocytes andthrombocytes but not erythrocytes, presumably due to systemicinterferons, but no other obvious toxicities (FIG. 27). The ex vivoanalysis of spleen cells demonstrated potent activation of myeloid andplasmacytoid dendritic cells, NK cells, CD4 and CD8 T cells (FIG. 28).Activation of splenic NK cells was observed in wild-type andTLR7-deficient mice and required the presence of the type I IFNreceptor; NK cells showed ex vivo tumoricidal activity against B16melanoma cells (FIG. 29). Treatment with 3p-2.2 was associated withenhanced recruitment and activation of NK cells in the lungs (FIG. 20b,c).

Contribution of bcl-2-Silencing to Anti-Tumor Activity In Vivo

Confocal microscopy confirmed that fluorescently-labeled siRNA reachedhealthy lung tissue as well as metastases (FIG. 30 a). Bcl-2 wassilenced in tumor cells (FIG. 20 d) of tumor-bearing mice treated with3p-2.2 and OH-2.2 (FIG. 20 d and FIG. 30 b). Downregulation of Bcl-2 wasassociated with RNAi in vivo, as only the bcl-2 specific siRNAsgenerated a specific cleavage product via 5′-RACE (FIG. 20 e). Tunelstaining revealed massive apoptosis in mice treated with 3p-2.2 comparedto mice treated with control RNA, although the number of HMB45 positivetumor cells was much higher in the control-treated animals (FIG. 20 f).No Bcl-2 silencing or induction of apoptosis was seen in immune cellsubsets in vivo (FIG. 30 c) further supporting relative tumor cellselectivity.

Next, rescue experiments were performed to confirm that silencing ofbcl-2 contributes to the therapeutic activity of 3p-bcl-2-siRNA in vivo.B16 melanoma cells were stably transduced with a mutated bcl-2 cDNAspecifically designed to disrupt the target cleavage site of the siRNAanti-Bcl-2.2 without affecting the amino acid sequence of the bcl-2protein (FIG. 31). Expression of the mutated bcl-2 cDNA in B16 melanomacells (mut-B16) prevented bcl-2 silencing and apoptosis induction by3p-2.2 but not by 3p-2.4 targeting bcl-2 mRNA at a different non-mutatedsite (FIGS. 21 a and 21 b, Table 7).

In vivo, 3p-2.4 and 3p-2.2 showed similar anti-tumor efficacy againstB16 melanoma lung metastases (FIG. 21 c) and induced similar systemiclevels of IFN-α (FIG. 21 d). In vivo rescue experiments with WT-B16 andMut-B16 confirmed that the therapeutic effect of OH-2.2 and 3p-2.2depended in part on bcl-2 gene silencing in tumor cells (FIG. 21 e).Taken together, these results provide evidence that both gene silencingand RIG-I-dependent activation of innate immunity contribute to theanti-tumor activity of 3p-2.2 in the B16 melanoma model in vivo.

Next we confirmed the anti-tumor activity of 3p-siRNA in a new geneticmelanoma model which is based on important events in the molecularpathogenesis of human melanoma and much more closely mimics the clinicalsetting⁵⁷. Primary melanomas derived from the skin of HGF/CDK4^(R24C)mice were serially transplanted to groups of CDK4^(R24C) mice.Repetitive peritumoral injections with 3p-2.2 led to a significant delayin tumor growth (FIG. 22 a, left panel) associated with downregulationof Bcl-2 but not Mcl-1, Bcl-xL, Puma or Bim in melanoma cells in vivo(FIG. 22 a, right panel). In addition, 3p-2.2 also showed significantanti-tumor efficacy in a colon carcinoma model in Balb/C mice (FIG. 22b, left panel), associated with systemic production of IFN-α anddownregulation of Bcl-2 expression (FIG. 22 b, right panel, FIG. 32).

Finally we designed human anti-Bcl-2 siRNA (OH-h2.2 and 3p-h2.2) andtested them in a human melanoma cell line (1205 Lu). Treatment of 1205Lu with 3p-h2.2 and 3p-GC, but not with OH-h2.2 or the control RNA wasable to induce IFN-β (FIG. 22 c). Both OH-h2.2 and 3p-h2.2 stronglyreduced Bcl-2 protein levels (FIG. 22 d). Similar to 3p-2.2 in murineB16 melanoma cells, 3p-h2.2 strongly promoted apoptosis (FIG. 22 d) anddecreased viability of human melanoma cells, while the pro-apoptoticactivity was less pronounced in primary human melanocytes and primaryhuman fibroblasts both isolated from skin of healthy donors (FIG. 22 e).

Results

The results of this study demonstrate that systemic administration of asiRNA deliberately designed to silence Bcl-2 and to activate RIG-I(3p-2.2) strongly inhibits tumor growth reflected by massive tumorapoptosis on a histological level. This response requires type I IFN andNK cells, and is associated with the induction of systemic Th1 cytokines(IFN-α, IL-12p40, IFN-γ), direct and indirect activation of immune cellsubsets and with recruitment and activation of NK cells in lung tissue.Furthermore, sequence-specific silencing of Bcl-2 contributes toanti-tumor efficacy of 3p-2.2. This is evidenced by site-specificcleavage of Bcl-2 mRNA, sequence-dependent rescue studies in vitro andin vivo, and downregulation of Bcl-2 protein on a single cell level inlung tumor cells.

Due to its molecular design, siRNA 3p-2.2 contains two distinctfunctional properties: a) gene silencing and b) RIG-I activation. Anumber of biological effects caused by these two properties maycooperate to provoke the beneficial anti-tumor response in vivo: a)silencing of Bcl-2 may induce apoptosis in cells that depend on Bcl-2overexpression (such as tumor cells), and via the same mechanism may aswell sensitize tumor cells towards innate effector cells⁴⁷: b) RIG-Iactivation: RIG-I is expressed in immune cells as well as in non-immunecells including tumor cells. Consequently, activation of RIG-I leads todirect and indirect activation of immune cell subsets, but also provokesinnate responses directly in tumor cells such as the production of typeI IFNs or chemokines, and directly promotes apoptosis. These activitiesact in concert to elicit the potent anti-tumor effect seen (for aschematic overview of the potential antitumor mechanism elicited by3p-siRNA see FIG. 33).

In fact, our data provide experimental evidence that B16 melanoma cellsexpress RIG-I and that 3p-2.2 not only silences Bcl-2 but alsostimulates type I IFN, IP-10, MHC I, and induces apoptosis directly intumor cells. Furthermore, we demonstrate that silencing of Bcl-2 intumor cells does not require RIG-I ligand activity (OH-2.2, samesequence as 3p-2.2 but no triphosphate), and that RIG-I effects areindependent of Bcl-2 silencing activity (3p-MM and 3p-GC, triphosphatebut no silencing). Importantly, compared to the respective singleactivities, our data demonstrate synergistic induction of tumor cellapoptosis in vitro and synergistic inhibition of Bcl-2 and induction ofapoptosis in tumor cells in vivo when both silencing and RIG-I activityare in place (3p-2.2 compared to OH-2.2, 3p-MM or 3p-GC alone).

The lower anti-tumor response of 3p-MM and 3p-GC compared to 3p-2.2 invivo, the lack of Bcl-2 inhibition in tumor cells in vivo by the RIG-Iligand (3p-GC) alone, and the sequence-specific rescue experimentsconfirm that gene silencing is a key functional property of 3p-2.2.Likewise, the lower overall anti-tumor response to anti-Bcl-2 siRNA(OH-2.2) despite strong inhibition of Bcl-2 in tumor cells in vivohighlights the importance of the innate contribution. Each mechanism byitself is not as potent to suppress tumor growth in vivo as thecombination. This is supported by the rescue experiments which showedthat apoptosis induced by OH-2.2 depended completely on Bcl-2 whileapoptosis induced by 3p-2.2 depended only in part on Bcl-2 genesilencing.

A key question is how systemic administration of the combinatorial RNAmolecule 3p-2.2 can result in the tumor specificity observed. Followingintravenous injection, fluorescently-labeled RNA complexed withpolyethylenimine (PEI) was enriched in lungs but also liver, spleen andkidney (data not shown). Thus, in our study RNA delivery is not targetedto the tumor. Nevertheless, tumor specific apoptosis induction is seenwhich may be explained by a cooperation of the following threemechanisms: first, melanoma cells express high levels of Bcl-2 toprevent spontaneous tumor cell apoptosis^(50,52), while in normal cellsall checkpoints of apoptosis are intact and inhibition of Bcl-2 alone isnot sufficient for apoptosis induction. This is supported by our datacomparing B16 tumor cells and fibroblasts as well as human melanomacells and primary human melanocytes. Second, in our hands RIG-Iactivation is sufficient to induce apoptosis in B16 tumor cells andhuman melanoma cells but not in normal cells such as fibroblasts, humanfibroblasts or human melanocytes. Third, B16 melanoma cells are muchmore sensitive to killing by activated NK cells, strongly upregulate MHCI expression and secrete high amounts of IP-10 only after transfectionwith 3p-siRNA. We therefore hypothesize that RIG-1-mediated activationof the type I IFN system in tumor cells leads to changes on the cellsurface that predisposes these cells for NK cell attack and destruction,similar to what was proposed by Stetson and Medzhitov⁵³.

Our studies show that treatment with 3p-siRNA can be extended to othermodels of tumorigenesis. We found anti-tumor activity against melanomasderived from primary cutaneous tumors in HGF×CDK4^(R24C) mice. TheHGF×CDK4^(R24C) mouse melanoma model resembles the expected clinicalsituation in melanoma patients much more closely, first becausemelanomas arise as a consequence of genetic alterations similar to thoseobserved in patients and second because melanomagenesis can be promotedby UV irradiation. Repeated administration of 3p-2.2 resulted in asignificant delay in tumor growth in this model. We also observedanti-tumor efficacy of 3p-siRNA in a syngeneic colon carcinoma model inBalb/c mice. Furthermore, we provide evidence that the approach can beadapted to the human system. A Bcl-2-specific 3p-siRNA mediated bothgene silencing and RIG-I activation in human melanoma cells leading toapoptosis, whereas melanocytes and fibroblasts were resistant toapoptosis induction. Based on these observations, the principles of thisapproach show promise for clinical translation.

The gene silencing activity of such combinatorial 3p-siRNA molecules canbe directed to any given molecularly defined genetic event that governstumor cell survival. A combination of siRNA sequences selected fordifferent tumor-related genes is feasible. New targets identified byfunctional screening in tumor cells can directly be imported into thiscombinatorial RNA system. This will advance our ability to attack thetumor from different biological angles which we think is required toeffectively counteract tumor cell survival, plasticity, and immuneescape. Despite the relative tumor specificity seen in our study, thisstrategy will be further improved by targeted delivery of the RNA totumor tissue.

REFERENCES

-   1. Kawai T, Akira S. Nat Immunol 2006; 7(2):131-7.-   2. Alexopoulou L et al. Nature 2001; 413(6857):732-8.-   3. Diebold S S et al. Science 2004; 303(5663):1529-31.-   4. Heil F et al. Science 2004; 303(5663):1526-9.-   5. Hornung V et al. Nat Med 2005; 11(3):263-70.-   6. Hemmi H et al. Nature 2000; 408(6813):740-5.-   7. Matsumoto M et al. J Immunol 2003; 171(6):3154-62.-   8. Nishiya T, DeFranco A L. J Biol Chem 2004; 279(18):19008-17.-   9. Latz E et al. Nat Immunol 2004; 5(2):190-8.-   10. Kato H et al. Nature 2006; 441(7089):101-5.-   11. Yoneyama M et al. Nat Immunol 2004; 5(7):730-7.-   12. Kato H et al. Immunity 2005; 23(1):19-28.-   13. Lau C M et al. J Exp Med 2005; 202(9):1171-7.-   14. Gitlin L et al. Proc Natl Acad Sci USA 2006; 103(22):8459-64.-   15. Hornung V et al. Science 2006; 314(5801):994-7.-   16. Marques J T et al. Nat Biotechnol 2006; 24(5):559-65.-   17. Judge A D et al. Nat Biotechnol 2005; 23(4):457-62.-   18. Sioud M. Eur J Immunol 2006; 36(5):1222-30.-   19. WO 2008/017473-   20. Kim D H et al. Nat Biotechnol 2004; 22:321-5.-   21. US 2006/0178334-   22. WO 2003/086280-   23. Reynold et al. Nat Biotechnol 2004; 22:326-30.-   24. Takahasi K et al. Molecular Cell 2008; 29:1-13.-   25. Pichlmair A et al. Science 2006; 314:997-1001.-   26. Cui S et al. Molecular Cell 2008; 29:169-179.-   27. Ludwig J & Eckstein F J Org Chem 1989; 54:631-635.-   28. WO 2007/031319-   29. WO 2007/031322-   30. Gondai T et al. Nucleic Acids Res 36(3):e18.-   31. Haas T et al. (2008) Immunity 28:315-323.-   32. Latz E et al. (2007) Nat Immunol 8:772-779.-   33. Weber F et al. (2006) J Virol 80:5059-5064.-   34. Loo Y M et al. (2008) J Virol 82:335-345.-   35. Bonin M et al. (2000) RNA 6:563-570.-   36. Hofacker I L et al. (2004) Bioinformatics 20:1495-1499.-   37. Portela A & Digard P (2992) J Gen Virol 83:723-734.-   38. Hanahan, D. & Weinberg, R. A. (2000) Cell 100, 57-70-   39. Bui, J. D. & Schreiber, R. D. (2007) Curr Opin Immunol 19,    203-8.-   40. Rubin, B. P., Heinrich, M. C. & Corless, C. L. (2007) Lancet    369, 1731-41-   41. Curiel, T. J. (2007) J Clin Invest 117, 1167-74-   42. Uno, T. et al. (2006) Nat Med 12, 693-8-   43. Obeid, M. et al. (2007) Nat Med 13, 54-61-   44. Schlee, M., Hornung, V. & Hartmann, G. (2006) Mol Ther 14,    463-70-   45. Pei, Y. & Tuschl, T. (2006) Nat Methods 3, 670-6-   46. de Fougerolles, A., Vornlocher, H. P., Maraganore, J. &    Lieberman, (2007) J. Nat Rev Drug Discov 6, 443-53-   47. Pichlmair, A. et al. (2006) Science 314, 997-1001.-   48. Yoneyama, M. & Fujita, T. (2007), J Biol Chem 282, 15315-8-   49. Yoneyama, M. & Fujita, T. (2007) J Biol Chem 282, 15315-8-   50. Miller, A. J. & Mihm, M. C., Jr. (2006) N Engl J Med 355, 51-65-   51. Danial, N. N. & Korsmeyer, S. J. (2004) Cell 116, 205-19-   52. McGill, G. G. et al. (2002) Cell 109, 707-18-   53. Stetson, D. B. & Medzhitov, R. (2006) J Exp Med 203, 1837-41.-   54. Mocikat, R. et al (2003). Immunity 19, 561-9-   55. Muller, U. et al. (1994), Science 264, 1918-21-   56. Kamphuis, E. et al (2006), Blood 108, 3253-61.-   57. Tormo, D. et al. (2006), Cancer Res 66, 5427-35.

1. An oligonucleotide preparation comprising an essentially homogenouspopulation of an oligonucleotide, wherein the oligonucleotide has atleast one blunt end, wherein the oligonucleotide comprises at least 1ribonucleotide at the 5′ end at the blunt end, wherein the blunt endbears a 5′ triphosphate attached to the most 5′ ribonucleotide, whereinthe 5′ triphosphate is free of any cap structure, wherein the blunt endis an end of a fully double-stranded section, and wherein the fullydouble-stranded section is at least 19, base pairs in length, wherein(i) other end of the oligonucleotide comprises a 5′ or 3′ overhang, (ii)other end of the oligonucleotide is a blunt end that does not bear a 5′triphosphate, or (iii) the oligonucleotide is a single-strandoligonucleotide having a stem-and-loop structure and wherein thedouble-stranded section is the stem of the stem-and-loop structure. 2.(canceled)
 3. (canceled)
 4. The oligonucleotide preparation of claim 1,wherein the oligonucleotide comprises at least one inosine.
 5. Theoligonucleotide preparation of claim 1, wherein the most 5′ribonucleotide with the triphosphate attached to is selected from thegroup consisting of A, G and U.
 6. The oligonucleotide preparation ofclaim 1, wherein the sequence of the first 4 ribonucleotides at the 5′end bearing the 5′-triphosphate is selected from the group consistingof: AAGU, AAAG, AUGG, AUUA, AACG, AUGA, AGUU, AUUG, AACA, AGAA, AGCA,AACU, AUCG, AGGA, AUCA, AUGC, AGUA, AAGC, AACC, AGGU, AAAC, AUGU, ACUG,ACGA, ACAG, AAGG, ACAU, ACGC, AAAU, ACGG, AUUC, AGUG, ACAA, AUCC, AGUC,wherein the sequence is in the 5′->3′ direction,
 7. The oligonucleotidepreparation of claim 1, wherein the oligonucleotide is free ofmodifications selected from the group consisting of pseudouridine,2-thiouridine, 2′-fluorine-dNTP.
 8. The oligonucleotide preparation ofclaim 1, wherein the most 3′ nucleotide which base pairs with the most5′ ribonucleotide bearing the 5′ triphosphate at the blunt end is2′-O-methylated.
 9. The oligonucleotide preparation of claim 1, whereinthe oligonucleotide comprises at least one structural motif recognizedby at least one of TLR3, TLR7, TLR8 and TLR9.
 10. The oligonucleotidepreparation of claim 1, wherein the oligonucleotide has targetgene-silencing activity.
 11. The oligonucleotide preparation of claim10, wherein the oligonucleotide has both target gene-silencing activityand the ability of RIG-I activation.
 12. The oligonucleotide preparationof claim 10, wherein the target gene is Bcl-2.
 13. A pharmaceuticalcomposition comprising at least one oligonucleotide preparation of claim1 and a pharmaceutically acceptable carrier.
 14. The pharmaceuticalcomposition of claim 13, further comprising at least one agent selectedfrom an immunostimulatory agent, an antigen, an anti-viral agent, ananti-bacterial agent, an anti-tumor agent, retinoic acid, IFN-α, andIFN-β.
 15. (canceled)
 16. (canceled)
 17. (canceled)
 18. (canceled) 19.An in vitro method for inducing type I IFN production in a cell,comprising the steps of: (a) mixing at least one oligonucleotidepreparation of claim 1 with a complexation agent; and (b) contacting acell with the mixture of (a), wherein the cell expresses RIG-I. 20.(canceled)
 21. An oligonucleotide preparation comprising an essentiallyhomogenous population of a single-strand oligonucleotide, wherein theoligonucleotide has a nucleotide sequence which is 100% complementary tothe nucleotide sequence between nucleotides 2+m and 2+m+n at the 5′ endof the genomic RNA of a negative single-strand RNA virus, wherein m andn are independently positive integers, wherein m is equal to or greaterthan 1 and is less than or equal to 5, and wherein n is equal to orgreater than
 12. 22. The oligonucleotide preparation of claim 20,wherein the negative single-strand RNA virus is selected from influenzaA virus, Rabies virus, Newcastle disease virus (NDV), vesicularstomatitis virus (VSV), Measles virus, mumps virus, respiratorysyncytial virus (RSV), Sendai virus, Ebola virus, or Hantavirus.
 23. Apharmaceutical composition comprising at least one oligonucleotidepreparation of claim 20 and a pharmaceutically acceptable carrier. 24.(canceled)
 25. (canceled)
 26. (canceled)
 27. (canceled)
 28. (canceled)29. (canceled)
 30. (canceled)
 31. (canceled)
 32. A method for enhancingthe type I IFN-inducing activity of an oligonucleotide, wherein theoligonucleotide has at least one blunt end and comprises at least 1ribonucleotide at the 5′ end at the blunt end, wherein the blunt endbears a 5′ triphosphate attached to the most 5′ ribonucleotide, whereinthe 5′ triphosphate is free of any cap structure, and wherein the bluntend is followed by a fully double-stranded section which is at least 19base pair (bp) in length, comprising the step of 2′-O-methylating themost 3′ nucleotide which base pairs with the most 5′ ribonucleotidebearing the 5′ triphosphate at the blunt end.
 33. A method for reducingthe type I IFN-inducing activity of an oligonucleotide, wherein theoligonucleotide has at least one blunt end and comprises at least 1ribonucleotide at the 5′ end at the blunt end, wherein the blunt endbears a 5′ triphosphate attached to the most 5′ ribonucleotide, whereinthe 5′ triphosphate is free of any cap structure, and wherein the bluntend is followed by a fully double-stranded section which is at least 19base pair (bp) in length, comprising the step of 2′-O-methylating anucleotide which is not the most 3′ nucleotide which base pairs with themost 5′ ribonucleotide bearing the 5′ triphosphate at the blunt end. 34.The method of claim 33, wherein the nucleotide to be 2′-O-methylated isthe nucleotide immediately 5′ to the most 3′ nucleotide which base pairswith the most 5′ ribonucleotide bearing the 5′ triphosphate at the bluntend.
 35. The oligonucleotide preparation of claim 7, wherein the2′-fluorine-dNTP is 2′-fluorine-dCTP or 2′-fluorine-dUTP.